General Description
Ceramide is an endogenous lipid component of a novel biochemical pathway termed the sphingomyelin pathway. Ceramide is produced in response to cellular stimulation by hormones, cytokines and antigens. Ceramide synthesis is mediated either by the salvage pathway by the acylation of sphingosine or sphingolipids hydrolysis or by
de novo pathway via dihydroceramide formation. Structurally, ceramides have a sphingoid base, a long-chain amino alcohol linked to fatty acid by an amide bond. Ceramide is generated by hydrolysis of sphingomyelin by sphingomyelinase.
Biochem/physiol Actions
Ceramide appears to have a role in mediating biological responses in a wide variety of cell types. Ceramide metabolites such as sphingosine and sphingosine-1-phosphate have potent biological activities of their own. They are directly involved in the proliferation and differentiation of skin cells and regulate skin barrier functionality. Ceramide based analogs are potential anti-tumor agents and are regarded as tumor suppressor lipid. Mechanisms for ceramide action involve regulation of protein phosphorylation via stimulation of a serine/threonine protein phosphatase, a proline-directed kinase and possibly other direct and/or indirect targets. Ceramide is emerging as an intracellular messenger than mediates effects on terminal differentiation and cell proliferation as well as apoptosis or cell death and cell-cycle arrest. The interrelationship of ceramide actions with other bioactive lipids and systems represents an area of active research.
