Phytosphingosine and C2-phytoceramide induce cell death and inhibit carbachol-stimulated phospholipase D activation in Chinese hamster ovary cells expressing the Caenorhabditis elegans muscarinic acetylcholine receptor

Sphingolipid metabolites, such as sphingosine and ceramide, are known to pl ay important roles in cell proliferation, differentiation and apoptosis, bu t the physiological roles of phytosphingosine (PHS) and phytoceramide (PHC) are poorly understood. In this study we investigated the effects of PI-IS, C2-PHC ((N-acetylPHS) and C6-PHC (N-hexanoylPHS) on cell growth and intrac ellular signalling enzymes. Treatment of Chinese hamster ovary (CHO) cells with PI-IS, C2-PHC or C6-PHC resulted in cell death in a time- and dose-dep endent manner. C2-PHC induced internucleosomal DNA fragmentation, whereas P HS or C6-PHC had little if any effect on DNA fragmentation under the same e xperimental conditions. Both PI-IS and C2-PHC inhibited carbachol-induced a ctivation of phospholipase D (PLD), but not of phospholipase C (PLC), in CH O cells expressing the Caenorhabditis elegans muscarinic acetylcholine rece ptor (mAChR), On the other hand, no significant effect of C6-PHC on PLD or PLC was observed, Our results show that PI-IS and C2-PHC exert strong cytot oxic effects on CHO cells and modulate the maChR-mediated signal transducti on pathway. (C) 2001 Federation of European Biochemical Societies. Publishe d by Elsevier Science B,V, All rights reserved.