A novel MALDI-FTICR imaging mass spectrometry (MALDI-IMS) workflow is described for on-tissue detection, spatial localization, and structural confirmation of low abundance bioactive
ceramides and other
sphingolipids. Increasingly, altered or elevated levels of
sphingolipids,
sphingolipid metabolites, and
sphingolipid metabolizing
enzymes have been associated with a variety of disorders such as diabetes,
obesity, lysosomal storage disorders, and
cancer.
Ceramide, which serves as a metabolic hub in
sphingolipid metabolism, has been linked to
cancer signaling pathways and to metabolic regulation with involvement in autophagy, cell-cycle arrest, senescence, and apoptosis. Using kidney tissues from a new
Farber disease mouse model in which
ceramides of all acyl chain lengths and other
sphingolipid metabolites accumulate in tissues, specific
ceramides and
sphingomyelins were identified by on-tissue isolation and fragmentation, coupled with an on-tissue digestion by
ceramidase or
sphingomyelinase. Multiple
glycosphingolipid species were also detected. The newly generated library of
sphingolipid ions was then applied to MALDI-IMS of human
lung cancer tissues. Multiple
tumor specific
ceramide and
sphingomyelin species were detected and confirmed by on-tissue
enzyme digests and structural confirmation. High-resolution MALDI-IMS in combination with novel on-tissue
ceramidase and
sphingomyelinase enzyme digestions makes it now possible to rapidly visualize the distribution of bioactive
ceramides and
sphingomyelin in tissues.