Treatment of neutral glycosphingolipid lysosomal storage diseases via inhibition of the ABC drug transporter, MDR1 - Cyclosporin A can lower serum and liver globotriaosyl ceramide levels in the Fabry mouse model

We have shown that the ABC transporter, multiple drug resistance protein 1 (MDR1, P-glycoprotein) translocates glucosyl ceramide from the cytosolic to the luminal Golgi surface for neutral, but not acidic, glycosphingolipid (GSL) synthesis. Here we show that the MDR1 inhibitor, cyclosporin A (CsA) can deplete Gaucher lyrnphoid cell lines of accumulated glucosyl ceramide and Fabry cell lines of globotriaosyl ceramide (Gb(3)) by preventing de novo synthesis. In the Fabry mouse model, Gb(3) is increased in the heart, liver, spleen, brain and kidney. The lack of renal glomerular Gb(3) is retained, but the number of verotoxin 1 (VT1)-staining renal tubules. and VT1 tubular targeting in vivo, is markedly increased in Fabry mice. Adult Fabry mice were treated with alpha-galactosidase (enzyme-replacement therapy, ERT) to eliminate serum Gb(3) and lower Gb(3) levels in some tissues. Serum Gb(3) was monitored using a VT1 ELISA during a post-ERT recovery phase biweekly intra peritoneal CsA. After 9 weeks, tissue Gb(3) content and localization were determined using VT1/TLC overlay and histochemistry. Serum Gb(3) recovered to lower levels after CsA treatment. Gb(3) was undetected in wild-type liver, and the levels of Gb(3) (but not gangliosides) in Fabry mouse liver were significantly depleted by CsA treatment. VT1 liver histochemistry showed Gb(3) accumulated in Kupffer cells, endothelial cell subsets within the central and portal vein and within the portal triad. Hepatic venule endothelial and Kupffer cell VT1 staining was considerably reduced by in vivo CsA treatment. We conclude that MDR1 inhibition warrants consideration as a novel adjunct treatment for neutral GSL storage diseases.