Ceramide activates a mitochondrial p38 mitogen-activated protein kinase: A potential mechanism for loss of mitochondrial transmembrane potential and apoptosis

This study examined the impact of ceramide, an intracellular mediator of apoptosis, on the mitochondria to test the hypothesis that ceramide utilized p38 MAPK in the mitochondria to alter mitochondrial potential and induce apoptosis. The capacity of ceramide to adversely affect mitochondria was demonstrated by the significant loss of mitochondrial potential (ΔΨ_m), indicated by a J-aggregate fluorescent probe, after embryonic chick cardiomyocytes were treated with the cell permeable ceramide analogue C₂-ceramide. p38 MAPK was identified in the mitochondrial fraction of the cell and p38 MAPK phosphorylation in this mitochondrial fraction of the cell occurred with ceramide treatment. In addition, SAPK phosphorylation and a decrease in ERK phosphorylation occurred in whole cell lysates after ceramide treatment. The p38 MAPK inhibitor SB 202190 but not the MEK inhibitor PD 98059 significantly inhibited ceramide-induced apoptosis and loss of ΔΨ_m. These data suggest that p38 MAPK is present in the mitochondria and its activation by ceramide indicates local signaling more directly coupled to the mitochondrial pathway in apoptosis. (Mol Cell Biochem 278: 39–51, 2005)