Toxic profile of bergamot essential oil on survival and proliferation of SH-SY5Y neuroblastoma cells

Cosmetic, pharmaceutical, food and confectionary industries make increasing use of plant extracts in their products. Despite the widespread use of products containing plant extracts, the mechanisms of their effects are not fully characterized. Bergamot essential oil (BEO; Citrus bergamia, Risso) is a well-known plant extract used in aromatherapy and it has analgesic, anxiolytic and neuroprotective effects in rodents. To elicit neuroprotection, BEO recruits Akt prosurvival pathways. However, Akt stimulates cell proliferation, which may also pose risks for health in case of prolonged use. To study the potential effects of BEO on survival and proliferation of dividing cells, we selected human SH-SY5Y neuroblastoma cells. BEO triggered concentration-dependent mitochondrial dysfunction, cytoskeletal reorganization, cell shrinkage, DNA fragmentation and both caspase-dependent and independent cell death. Analysis of cleavage products of poly-(ADP-ribose) polymerase (PARP) revealed caspase-3 activation, but also activation of additional protease families. As result of increased proteolytic activity, Akt protein levels decreased in BEO-treated cells. Our data show that BEO can be lethal for dividing cells by activating multiple pathways. While this may reduce the risk of unwanted cell proliferation after prolonged use, it does suggest a cautionary approach to the use of inappropriate dilutions of the oil that may cause cell death.