by inhibiting the ability of insulin to activate the insulin signal transduction pathway and/or via the activation of JNK. Substances known to induce ceramide generation Anandamide Ceramidase inhibitors Chemotherapeutic agents Fas ligand Endotoxin Homocysteine Heat Hydroxypalmitoyl Sphinganine Gamma interferon Ionizing radiation Matrix metalloproteinases Niacinamide Reactive oxygen species Sphingosine Tetrahydrocannabinol and other cannabinoids TNF-alpha 1,25 Dihydroxy vitamin D Mechanism by which ceramide signaling occurs Currently, the means by which ceramide acts as a signaling molecule are not clear. One hypothesis is that ceramide generated in the plasma membrane enhances membrane rigidity and stabilizes smaller lipid platforms known as lipid rafts, allowing them to serve as platforms for signalling molecules. Moreover, as rafts on one leaflet of the membrane can induce localized changes in the other leaflet of the bilayer, they can potentially serve as the link between signals from outside the cell to signals to be generated within the cell. Ceramide has also been shown to form organized large channels traversing the mitochondrial outer membrane. This leads to the egress of proteins from the intermembrane space. Uses Ceramides may be found as ingredients of some topical skin medications used to complement treatment for skin conditions such as eczema. They are also used in cosmetic products such as some soaps, shampoos, skin creams, and sunscreens. Additionally, ceramides are being explored as a potential therapeutic in treating cancer. Ceramide in bacteria Ceramide is rarely found in bacteria. Bacteria of family Sphingomonadaceae, however, contain it. Ceramide phosphoethanolamine Ceramide phosphoethanolamine (CPE) is a sphingolipid consisted of a ceramide and a phosphoethanolamine head group. CPE is the major sphingolipid class in some invertebrates such as members of Drosophila. In contrast, mammalian cells contain only small amounts of CPE. References External links Lipids Ceramides