Enhancement of free fatty acid incorporation into phospholipids by cholineplus cytidine

Cytidine and choline, present in cytidine 5'-diphosphate choline (CDP-choli ne), are major precursors of the phosphatidylcholine found in cell membrane s and important regulatory elements in phosphatide biosynthesis. Administra tion of CDP-choline to rats increases blood and brain cytidine and choline levels; this enhances the production of endogenous CDP-choline which then c ombines with fatty acids (as diacylglycerol), to yield phosphatidylcholine. We examined the effect of providing cytidine and choline on incorporation of free fatty acids into phosphatidylcholine and other major phospholipids in PC12 cells. Addition of equimolar cytidine and choline (100-500 mu M) to [H-3]-arachidonic acid (50 mu M, 0.2 mu Ci, bound to bovine serum albumin) dose-dependently increased the accumulations of [H-3]-phosphatidylcholine (PtdCho), [H-3]-phosphatidylinositol (PtdIno) and [H-3]-phosphatidylethanol amine (PtdEtn) (by up to 27 +/- 3%, 16 +/- 3% and ii +/- 3%, respectively, means +/- S.E.M.). This effect was seen with 8-18 h of incubation. The inco rporation of [H-3]-oleic acid into [H-3]-PtdCho was even more enhanced (by up to 42 +/- 3%) as were the incorporations of [C-14]-choline and [H-3]-gly cerol. The effects of choline and cytidine were enhanced by 12-O-tetradecan oylphorbol-13-acetate(TPA, 1 mu M), which activates CTP:phosphocholine cyti dylyltransferase (CT) and facilitates choline uptake. Replacing choline by ethanolamine also enhanced the incorporation of [H-3]-arachidonic acid into [H-3]-PtdEtn, [H-3]-PtdIno and [H-3]-PtdCho. Arachidonic acid (10-200 mu M ) alone failed to affect the incorporation of [C-14]-choline into phosphati dylcholine. We suggest that the increases in phospholipid synthesis caused by concurrent cytidine and choline supplementation enhance the incorporatio n of arachidonic acid and certain other fatty acids into the major glycerop hospholipids. Removing these fatty acids as source of potentially toxic oxi dation products could contribute to the beneficial effects of CDP-choline i n treating stroke or other brain damage. (C) 1999 Elsevier Science B.V. All rights reserved.