Diatom-derived oxylipins induce cell death in sea urchin embryos activating caspase-8 and caspase 3/7

Abstract

Diatoms are an important class of unicellular algae that produce bioactive secondary metabolites withcytotoxic activity collectively termed oxylipins, including polyunsaturated aldehydes (PUAs), hydroxy-acids (HEPEs), oxo-acids and epoxyalcohols. Previous results showed that at higher concentrations, thePUA decadienal induced apoptosis on copepods and sea urchin embryos via caspase-3 activation; atlower concentrations decadienal affected the expression levels of the caspase-8 gene in embryos of thesea urchin Paracentrotus lividus. In the present work, we studied the effects of other common oxylip-ins produced by diatoms: two PUAs (heptadienal and octadienal) and four hydroxyacids (5-, 9- 11- and15-HEPE) on P. lividus cell death and caspase activities. Our results showed that (i) at higher concentra-tions PUAs and HEPEs induced apoptosis in sea urchin embryos, detected by microscopic observationand through the activation of caspase-3/7 and caspase-8 measured by luminescent assays; (ii) at lowconcentrations, PUAs and HEPEs affected the expression levels of caspase-8 and caspase-3/7 (isolated forthe first time here in P. lividus) genes, detected by Real Time qPCR. These findings have interesting impli-cations from the ecological point of view, given the importance of diatom blooms in nutrient-rich aquaticenvironments