Molecular mechanisms of euplotin C-induced apoptosis: involvement of mitochondrial dysfunction, oxidative stress and proteases.
The metabolite euplotin C (EC), isolated from the marine ciliate Euplotes crassus, is a powerful cytotoxic and pro-apoptotic agent in tumour cell lines. For instance, EC induces the rapid depletion of ryanodine Ca(2+) stores, the release of cytochrome c from the mitochondria, and the activation of caspase-3, leading to apoptosis. The purpose of this study was to gain further insight into the mechanisms of EC-induced apoptosis in rat pheochromocytoma PC12 cells. We found that EC increases Bax/Bcl-2 ratio and that Bax is responsible of the EC-induced dissipation of the mitochondrial membrane potential (Deltapsi(m)). In addition, EC induces the generation of reactive oxygene species (ROS) without involvement of p53. The inhibition of ROS generation prevents, at least in part, the pro-apoptotic effects of EC as well as the effects of EC on Bax, Deltapsi(m) and intracellular free Ca(2+), indicating a cross-talk between different pathways. However, definition of the effector cascade turns out to be more complex than expected and caspase-independent mechanisms, acting in parallel with caspases, should also be considered. Among them, EC increases the expression/activity of calpains downstream of ROS generation, although calpains seem to exert protective effects.
Cervia
Davide
D
Department of Environmental Sciences, University of Tuscia, Viterbo, Italy. d.cervia@unitus.it
Garcia-Gil
Mercedes
M
Simonetti
Elisa
E
Di Giuseppe
Graziano
G
Guella
Graziano
G
Bagnoli
Paola
P
Dini
Fernando
F
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002154:Calpain / Q000235:genetics / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects* / Q000201:enzymology / Q000502:physiology; D018384:Oxidative Stress / Q000187:drug effects*; D016716:PC12 Cells; D010447:Peptide Hydrolases / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D012717:Sesquiterpenes / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D051028:bcl-2-Associated X Protein / Q000378:metabolism
D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D012717:Sesquiterpenes; D051028:bcl-2-Associated X Protein; C493253:euplotin C; D010447:Peptide Hydrolases; D002154:Calpain