Effects of Synthetic Sphingosine-1-Phosphate Analogs on Cytosolic Phospholipase A2α–Independent Release of Arachidonic Acid and Cell Toxicity in L929 Fibrosarcoma Cells: the Structure–Activity Relationship

Abstract

Abstract. Sphingolipid metabolites including ceramide, sphingosine, and their phosphorylated products [sphingosine-1-phosphate (S1P) and ceramide-1-phosphate] regulate cell functions including arachidonic acid (AA) metabolism and cell death. The development of analogs of S1P may be useful for regulating these mediator-induced cellular responses. We synthesized new analogs of S1P and examined their effects on the release of AA and cell death in L929 mouse fibrosarcoma cells. Among the analogs tested, several compounds including DMB-mC11S [dimethyl (2S,3R)-2-tert-butoxycarbonylamino-3-hydroxy-3-(3'-undecyl)phenylpropyl phosphate] and DMB-mC9S [dimethyl (2S,3R)-2-tert-butoxycarbonylamino-3-hydroxy-3-(3'-nonyl)phenylpropyl phosphate] released AA within 1 h and caused cell death 6 h after treatment. The release of AA was observed in C12 cells [a L929 variant lacking a type α cytosolic phospholipase A 2 (cPLA 2 α)] and L929-cPLAα-siRNA cells (L929 cells treated with small interference RNA for cPLA 2 α). Treatment with pharmacological inhibitors of secretory and Ca 2+ -independent PLA 2 s decreased the DMB-mC11S-induced release of AA. The effect of the S1P analogs tested on the release of AA was comparable to that on cell death in L929 cells, and a high correlation coefficient was observed. Two analogs lacking a butoxycarbonyl moiety phenylpropyl phosphate] and DMAm-mC11S [dimethyl (2S,3R)-2-amino-3-hydroxy-3-(3'-undecyl)phenylpropyl phosphate)] had inhibitory effects on the release of AA and cell toxicity induced by DMB-mC11S. Synthetic phosphorylated lipid analogs may be useful for studying PLA 2 activity and its toxicity in cells.[ Supplementary Fig. 1: available only at http://dx

Sphingomyelin Regulates the Activity of Secretory Phospholipase A2 in the Plasma Membrane

“…AA and its metabolites have been established to show cytotoxicity and be involved in various diseases such as neurological disorders and liver and myocardial injuries [Farooqui et al, ; Yagami et al, ]. Previously, we reported that exogenously added AA and AA released endogenously by Ca 2+ ‐dependent cytosolic PLA 2 and by other PLA 2 s caused cell death in L929 fibrosarcoma cells [Kurosawa et al, ; Shimizu et al, ] and CHO cells [Nakamura et al, ]. Several sPLA 2 such as human sPLA 2 ‐IB and ‐IIA, and sPLA 2 ‐III from bee venom have been shown to cause cell death including apoptosis in neuronal cells [Yagami et al, , ; DeCoster, ].…”