C6 ceramide is a cell-permeable analog of naturally occurring ceramides. With a longer carbon chain than C2 ceramide, it is somewhat more hydrophobic, and may more closely mimic the effects of natural ceramides.{2756} C6 ceramide mediates many diverse biological activities including apoptosis,{3988} activation of protein phosphatase 2A,{2756,2757} and inhibition of the mitochondrial respiratory chain.{5031} It also enhances the expression of COX-2 in rat granulosa cells{5473} and stimulates the growth of bovine aortic smooth muscle cells.{3512} C6 ceramide acts in neuronal axons to inhibit neurite growth.{5302}