Metabolism of the unnatural anticancer lipid safingol, l-threo-dihydrosphingosine, in cultured cells

Abstract

We studied the metabolism of radioactively labeled safingol ( L -threo-dihydrosphingosine) in primary cultured neurons, B104 neuroblastoma cells, and Swiss 3T3 fibroblasts, and compared it to that of its natural stereoisomer D -erythro -dihydrosphingosine. Both sphingoid bases are used as biosynthetic precursors for complex sphingolipids, albeit to different rates. Whereas a considerable amount of the natural sphingoid base is also directed to the catabolic pathway (20-66%, cell type dependent), only a minor amount of the nonnatural safingol is subjected to catabolic cleavage, most of it being N -acylated to the respective stereochemical variant of dihydroceramide. Interestingly, N -acylation of safingol to L -threo -dihydroceramide is less sensitive to fumonisin B1 than the formation of the natural D -erythro -dihydroceramide. In addition, safingol-derived L -threo-dihydroceramide, unlike its physiologic counterpart, is not desaturated. Most of it either accumulates in the cells (up to 50%) or is used as a biosynthetic precursor of the respective dihydrosphingomyelin (up to 45%). About 5% is, however, glucosylated and channeled into the glycosphingolipid biosynthetic pathway. Our results demonstrate that, despite its nonnatural stereochemistry, safingol is recognized and metabolized preferentially by enzymes of the sphingolipid biosynthetic pathway. Furthermore, our data suggest that the cytotoxic potential of safingol is reduced rather than enhanced via its metabolic conversion. -Dragusin, M., C. Gurgui, G. Schwarzmann, J. Hoernschemeyer, and G. van Echten-Deckert. Metabolism of the unnatural anticancer lipid safingol, L -threo -dihydrosphingosine, in cultured cells.

Cytotoxicity of sphingoid marine compound analogs in mono- and multilayered solid tumor cell cultures

“…These values were comparable to 3.8-8.6 µM, which is the activity reported for safingol against a panel of six HNSCC cell lines including 22B [28]. It has been shown that despite its nonnatural stereochemistry, safingol is recognized and metabolized preferentially by enzymes of the sphingolipid biosynthetic pathway [29].…”

Fenretinide Cytotoxicity for Ewing’s Sarcoma and Primitive Neuroectodermal Tumor Cell Lines Is Decreased by Hypoxia and Synergistically Enhanced by Ceramide Modulators

“…We and others have demonstrated that safingol is metabolized into Lthreo-dihydroceramide and/or L-threo-ceramide variants, both in vitro (14, 74 -77) and in vivo (78), with some disagreement between the data, perhaps due to species or cell line type variation. L-threodihydroceramide and/or L-threo-ceramide was incorporated into dihydrosphingomyelin or sphingomyelin but not readily glucosylated, thus demonstrating stereo-specific metabolic restrictions (14,74,75,78). Because we and others have demonstrated that high levels of one or both of these L-threo sphingolipids accumulate even at low, nontoxic safingol concentrations in vitro (14), it is possible that L-threo sphingolipids may synergize the cytotoxicity of native de novo-generated ceramide species, including dihydroceramides (79,80), by specific interference with their catabolism or may interfere with the ability of native ceramide species to activate atypical protein kinase Cs.…”

Sphingolipids in Anticancer Therapy

“…It was shown that despite its nonnatural stereochemistry, safingol (39) was recognized and metabolized preferentially by enzymes of the sphingolipid biosynthetic pathway [96]. Safingol (39) was mainly metabolized to dihydroceramide (4 ) and dihydrosphingomyelin, whereas most of its physiological counterpart sphinganine (3) was transformed in cultured cells into fatty acids, sphingomyelin, and complex gangliosides.…”