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Synthesis of 1-acyl-2-acetyl-sn-glycero-3-phosphocholine by an enriched preparation of the human lung mast cell.

Massimo Triggiani,Walter C. Hubbard,Floyd H. Chilton

Published 1990 in Journal of Immunology

ABSTRACT

Our study has examined the synthesis of platelet activating factor (PAF; 1-0-alkyl-2-acetyl-sn-glycero-3-phosphocholine) and of structurally related molecules by an enriched preparation (greater than 70%) of the human lung mast cell (HLMC) in response to immunologic stimulation. Upon activation with anti-IgE, HLMC incorporated exogenously provided acetate into a phospholipid that migrated with authentic PAF on TLC. The formation of this product in HLMC occurred concomitantly with histamine and leukotriene C4 release. Further analysis of this phospholipid revealed that 1-acyl-2-acetyl-sn-glycero-3-phosphocholine (GPC) and not 1-alkyl-2-acetyl-GPC was the major 1-radyl-2-acetyl-GPC subclass formed during cell activation. The presence of 1-alkyl-2-acetyl-GPC was confirmed by negative ion chemical ionization mass spectrometry. In addition to this product, anti-IgE-stimulated HLMC synthesized relatively small quantities of another 2-acetylated phospholipid migrating on TLC between phosphatidylcholine and phosphatidylinositol. The chromatographic characteristics of this product suggested that it is a subclass of 1-radyl-2-acetyl-sn-glycero-3-phosphoethanolamine. The catabolism of both 1-acyl-2-acetyl-GPC and 1-alkyl-2-acetyl-GPC was next examined to determine if the predominant formation of 1-acyl-2-acetyl-GPC over 1-alkyl-2-acetyl-GPC were metabolized by the HLMC at similar rates. There was, however, a qualitative difference in the metabolic products derived from the two phospholipids. 1-Alkyl-2-acetyl-GPC was rapidly inactivated by removal of the acetate moiety at the sn-2 position followed by rapid reacylation with arachidonate. By contrast, 1-acyl-2-acetyl-GPC was catabolized mainly by removal of the fatty acyl moiety at the sn-1 position. These data demonstrate the natural occurrence of PAF and at least two structurally similar molecules in anti-IgE stimulated HLMC. Furthermore, an analog containing an ester linkage at the sn-1 position, 1-acyl-2-acetyl-GPC, appears to be the major acetylated product synthesized under these conditions.

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