Mitochondrial cytochrome c release precedes transmembrane depolarisation and caspase-3 activation during ceramide-induced apoptosis of Jurkat T cells.
Whilst the role of ceramide, a second messenger of the sphingolipid family, in the initiation of receptor-mediated apoptosis is controversial, a growing body of evidence is emerging for a role of ceramide in the amplification of apoptosis via mitochondrial perturbations that culminate in the activation of execution caspases. Treatment of Jurkat T cells with the cell-permeable analog, C(2)-ceramide, resulted in the rapid onset of apoptosis as evidenced by Annexin V-FITC staining of externalised phosphatidylserine residues. Cells bearing this early apoptotic marker had a reduced mitochondrial transmembrane potential (Delta(Psi)m) that was preceded by the release of cytochrome c from mitochondria. Subsequent activation of caspase-3 provides the link between these ceramide-induced mitochondrial changes and execution caspases that ultimately result in the physical destruction of the cell. Collectively these results demonstrate that ceramide signalling results in caspase-mediated apoptosis via mitochondrial cytochrome c release and are further supportive of the role of ceramide in the amplification of apoptosis.