title: The secondary metabolite euplotin C induces apoptosis-like death in the marine ciliated protist Euplotes vannus.
abstract: The sesquiterpenoid euplotin C is a secondary metabolite produced by the ciliated protist Euplotes crassus and provides a mechanism for damping populations of potential competitors. Indeed, E. crassus is virtually resistant to its own product while different non-producer species representing an unbiased sample of the marine, interstitial, ciliate diversity are sensitive. For instance, euplotin C exerts a marked disruption of different homeostatic mechanisms in Euplotes vannus. We demonstrate by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay that euplotin C quickly decreases viability and mitochondrial function of E. vannus with a very high efficacy and at micromolar potency. In addition, euplotin C induces apoptosis in E. vannus as 4,6-diamino-2-phenylindole and terminal transferase dUTP nick end labeling staining show the rapid condensation and fragmentation of nuclear material in cells treated with euplotin C. These effects occur without detectable permeabilisation or rupture of cell membranes and with no major changes in the overall morphology, although some traits, such as vacuolisation and disorganized microtubules, can be observed by transmission electron microscopy. In particular, E. vannus show profound changes of the mitochondrial ultrastructure. Finally, we also show that caspase activity in E. vannus is increased by euplotin C. These data elucidate the pro-apoptotic role of euplotin C and suggest a mechanism for its impact on natural selection.
authors.affiliation: Department of Environmental Sciences, University of Tuscia, Viterbo, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Cervia
authors.forename: Graziano
authors.initials: G
authors.lastname: Di Giuseppe
authors.forename: Chiara
authors.initials: C
authors.lastname: Ristori
authors.forename: Davide
authors.initials: D
authors.lastname: Martini
authors.forename: Gabriella
authors.initials: G
authors.lastname: Gambellini
authors.forename: Paola
authors.initials: P
authors.lastname: Bagnoli
authors.forename: Fernando
authors.initials: F
authors.lastname: Dini
mesh_terms: D000818:Animals; D017209:Apoptosis; D002462:Cell Membrane / Q000648:ultrastructure; D053938:DNA Fragmentation; D016812:Euplotes / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D020287:In Situ Nick-End Labeling / Q000379:methods; D050296:Microbial Viability; D015388:Organelles / Q000648:ultrastructure; D012717:Sesquiterpenes / Q000633:toxicity*; D013778:Tetrazolium Salts / Q000378:metabolism; D013844:Thiazoles / Q000378:metabolism
chemical_list: D012717:Sesquiterpenes; D013778:Tetrazolium Salts; D013844:Thiazoles; C493253:euplotin C; C022616:thiazolyl blue