Ellagic acid induces a dose- and time-dependent depolarization of mitochondria and activation of caspase-9 and -3 in human neuroblastoma cells

The polyphenol ellagic acid is found in many natural food sources and has been proposed as a candidate compound for clinical applications due to its anti-oxidative capacity and as a potential anti-tumorigenic compound. The objective of the present study was to evaluate the sensitivity to and possible apoptosis mechanism induced by ellagic acid in neuronal tumor cells. As a model the human neuroblastoma SH-SY5Y cell line was used. The methods applied were bright field and phase contrast microscopy, XTT- and LDH-assays, western blot, and flow cytometric analysis of DNA degradation and mitochondrial membrane potential. Ellagic acid treatment was found to induce a reduction in cell number preceded by alterations of the mitochondrial membrane potential and activation of caspase-9 and -3, DNA-fragmentation and cell death by apoptosis. The apoptotic cell death studied was not due to anoikis since it was significant in the adherent fraction of the cells. We conclude that ellagic acid induces dose- and time-dependent apoptosis, at least partly by the mitochondrial pathway, in an embryonal neuronal tumor cell system. This finding is in agreement with previously reported data on adult carcinoma cells thus suggesting a more general effect of ellagic acid on tumor cells.