Chemistry, tissue and cellular distribution, and developmental profiles of neural sphingolipids

Sphingolipids constitute a class of lipids characterized by the presence of a long chain aminoalcohol (sphingoid base) and are particularly abundant in the nervous system. They include simple molecular species(sphingosine - or sphinganine -, sphingosine-1-phosphate, ceramide, ceramide-1-phosphate), and the ceramide containing complex sphingolipids (sphingomyelin, cerebrosides, sulfatides, neutral glycosphingolipids, acidic glycosphingolipids-gangliosides-, etc.). First, the chemical details are reported of both the naturally occurring sphingolipids, mostly present at the level of cellular membranes, and the synthetic sphingolipids, derivatives of sphingolipids, and mimetics of sphingolipids, that are extremely useful for biological investigations. Owing to the compositional complexity of sphingolipids, the analytical approaches employed for their detection, structural characterization, quantification, and “in situ” detection, are also briefly reviewed, in order to provide a basic and rationale background to investigators interested in the field. Then, the compositional profiles of sphingolipids in the nervous system of different animals, with particular emphasis to humans, are described, illustrating the analogies and differences, with regard to regional, cellular and subcellular localization of the individual sphingolipid species, with special attention to gangliosides, that display the wider array of composition. The differences in the long chain base and fatty acid composition, together with those in the saccharide composition in glycosphingolipids are also outlined, as a necessary chemical premise to understand the intricacy of the related metabolic pathways and to acknowledge the specifically distinct features of their functional implications. Finally, the developmental profiles of sphingolipids in the course of neural development and ageing in the different animals are described, illustrating common trends and peculiar differences among animals.