Glycosphingolipid depletion in Fabry disease lymphoblasts with potent inhibitors of glucosylceramide synthase

Background. Fabry disease is an inherited X-linked disorder resulting in the loss of activity of the lysosomal hydrolase α-galactosidase A and causing the clinical manifestations of renal failure, cerebral vascular disease, and myocardial infarction. The phenotypic expression of this disorder is manifest by the accumulation of glycosphingolipids containing α- galactosyl linkages, most prominently globotriaosylceramide. Methods. Based on quantitative structure activity studies, we recently reported two newly designed glucosylceramide synthase inhibitors based on 1-phenyl-2- palmitoylamino-3-pyrrolidino-1-propanol (P4). These inhibitors, 4'-hydroxy-P4 and ethylenedioxy-P4, were evaluated for their ability to deplete globotriaosylceramide and other glucosylceramide-based lipids in Fabry lymphocytes and were compared with N-butyldeoxynojirimycin, another reported glucosylceramide synthase inhibitor. Results. Concentrations as low as 10 nmol/L of 4'-hydroxy-P4 and ethylenedioxy-P4 resulted in 70 and 80% depletion, respectively, of globotriaosylceramide, with maximal depletion occurring at three days of treatment. There was no impairment of cell growth. In contrast, N-butyldeoxynojirimycin only minimally lowered globotriaosylceramide levels, even at concentrations as high as 10 μmol/L. Globotriaosylceramide depletion was confirmed by the loss of binding of FITC- conjugated verotoxin B subunit to the lymphoblasts. Conclusions. These findings suggest that selective glucosylceramide synthase inhibitors are highly effective in the depletion of globotriaosylceramide from Fabry cell lines. We suggest that these compounds have potential therapeutic utility in the treatment of Fabry disease.