C2 Phytoceramide is a bioactive semisynthetic sphingolipid that inhibits formyl peptide-induced oxidant release (IC50 = 0.38 µM) in suspended polymorphonuclear cells. It increases COX-2 protein levels 15-fold through ERK signaling. It induces death of keratinocytes (20% viability) with an ED50 value of 30 µM, the same concentration at which 35% of cells in a TUNEL assay are apoptotic. C2 Phytoceramide also has antiproliferative effects in CHO cells, with greater than 80% cytotoxicity achieved at a concentration of 20 µM, and induces internucleosomal DNA fragmentation. In addition, it inhibits the activation of phospholipase D (PLD) mediated by muscarinic acetylcholine receptors in vitro.