Abstract

Ceramide Metabolism in the Liver and its Role in Two Lysosomal Lipidoses - Drug-induced Phospholipidosis and Sandhoff Disease

Emma Lecommandeur, PhD Student, Department of Biochemistry, University of Cambridge

Owing to its role in regulating major cellular functions, ceramide metabolism has been studied in two lysosomal lipidoses, drug-induced phospholipidosis (DIPL) and Sandhoff disease (SD). Open-profiling of all detectable lipids was achieved using high-resolution mass spectrometry (MS), whilst targeted analysis of six specific ceramide species was performed by tandem MS using multiple reaction monitoring. Chloroquine DIPL was studied in Hep G2 cells and liver from rats, whilst SD was assessed in the liver from a mouse model. Although the total ceramide content was not affected by the lysosomal lipidoses, compared with the controls, the proportions of the different fatty acyl chain lengths in the pool of ceramides were changed, including a common increase in C16:0 ceramide. In the case of DIPL, the change to the composition of the ceramides was also accompanied by an alteration to the expression of the ceramide synthase genes, as measured by qPCR in both intact tissue and Hep G2 cells. These results demonstrate that ceramides are selectively affected by lysosomal lipidoses in liver according to their fatty acyl chain length, and this is associated with changes in ceramide synthases. These alterations may lead to changes in membrane morphology and affect a variety of cellular functions.