C2 ceramide is a cell-permeable analog of naturally occurring ceramides. It mediates many diverse biological activities, as do natural ceramides. These processes include differentiation of HL-60 cells,{2751} induction of apoptosis,{884} activation of protein phosphatase 2A,{2757} and inhibition of the mitochondrial respiratory chain.{5031} C2 ceramide also enhances the expression of COX-2 in human dermal fibroblasts{2759} and stimulates the growth of bovine aortic smooth muscle cells.{3512} The ability of C2 ceramide to destabilize membranes may be responsible for its inhibition of platelet aggregation.{6012}