Trifluoperazine stimulates the coordinate degradation of sphingomyelin and phosphatidylcholine in GH3 pituitary cells.
Prior studies demonstrated that 1,2-diacylglycerols stimulated degradation of the choline-containing phospholipids, phosphatidylcholine and sphingomyelin, in GH3 pituitary cells by a phospholipase A2 and a sphingomyelinase, respectively (Kolesnick, R. N. (1987) J. Biol. Chem. 262, 16759-16762). The present studies demonstrate that the phenothiazine trifluoperazine also stimulates degradation of these phospholipids. Trifluoperazine (25 microM) reduced phosphatidylcholine and sphingomyelin levels to 81 and 58% of control, respectively, after 30 min in cells labeled for 48 h with [3H] choline. Choline-containing metabolites were released specifically into the cytosolic fraction. The level of cytosolic phosphocholine, but not choline or CDP-choline, increased to 150% of control. These events were not mediated by inhibition of phosphatidylcholine synthesis. The level of 1,2-diacylglycerols, but not lysophosphatidylcholine or glycerol-3-phosphocholine, also increased. These data are most consistent with phosphatidylcholine degradation via a phospholipase C. Trifluoperazine-stimulated sphingomyelin degradation was accompanied by quantitative generation of ceramides consistent with activation of a sphingomyelinase. In contrast to trifluoperazine, choline-containing metabolites were released into the medium during stimulation by the 1,2-diacylglycerol 1,2-dioctanoyl-glycerol. Although both trifluoperazine and 1,2-dioctanoylglycerol increased ceramide levels, only 1,2-dioctanoylglycerol increased the sphingoid base level from 24 to 43 pmol/10(6) cells. Hence, trifluoperazine appears to deplete an intracellular pool of phosphatidylcholine and sphingomyelin by a different mechanism than 1,2-diacylglycerols. This is the first report of phenothiazine-induced degradation of choline-containing phospholipids.
Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York 10021.
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RN
Kolesnick
M R
MR
Hemer
D000818:Animals; D002460:Cell Line; D002518:Ceramides / Q000378:metabolism; D002794:Choline / Q000037:antagonists & inhibitors; D003600:Cytosol / Q000378:metabolism; D004075:Diglycerides / Q000494:pharmacology; D007700:Kinetics; D010713:Phosphatidylcholines / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*; D010902:Pituitary Gland / Q000378:metabolism*; D051381:Rats; D013109:Sphingomyelins / Q000378:metabolism*; D014268:Trifluoperazine / Q000494:pharmacology*
D002518:Ceramides; D004075:Diglycerides; D010713:Phosphatidylcholines; D013109:Sphingomyelins; D014268:Trifluoperazine; D002794:Choline