Use of an Inhibitor of Glucosylceramide Synthesis, D-1-Phenyl-2-decanoylamino-3-morpholino-1 -propanol

Methods for the synthesis, purification, and use of an inhibitor of glucosylceramide synthesis (PDMP or D-1-phenyl-2-decanoylamino-3-morpholino-1-propanol) are given. The inhibitor is effective with a variety of cells and animals in producing a depletion of glucosylceramide. Because this cerebroside is the precursor of hundreds of other glycolipids, depletion of all of these compounds also takes place as each one is degraded by hydrolases. Use of PDMP causes accumulation of ceramide, the lipoidal precursor of glucosylceramide. Some of this simple sphingolipid is diverted to the synthesis of sphingomyelin and some, via hydrolysis, to formation of sphingols (sphingoid bases). The above changes in the biosynthesis of glycolipids result in pronounced effects on cells: slowing of growth, increased activity of the phospholipase C that catalyzes phosphatidylinositol bisphosphate hydrolysis, accumulation of N,N-dimethylsphingosine (an inhibitor of protein kinase C), accumulation of diacyiglycerol (an activator of PKC), and reduction of the ability to bind to extracellular matrix proteins. PDMP is rapidly absorbed and released by cells. In mice, it is metabolized by a microsomal monooxygenase and the products are excreted. The degradative process can be blocked by inhibitors of cytochrome P-450, such as piperonyl butoxide, cimetidine, and fluconazole. Understanding these properties permits the use of PDMP in both in vitro and in vivo studies in which glycolipids may exhibit important biological effects. Two recent examples of the in vitro and in vivo use of PDMP are provided.