Combined Effects of Diatom-Derived Oxylipins on the Sea Urchin Paracentrotus lividus.

Roberta Esposito,Luisa Albarano,Giovanni Libralato,Nadia Ruocco,Loredana Manfra,Maria Costantini,Adrianna Ianora

doi:10.3390/ijms21030719

Abstract

Oxylipins are diatom-derived secondary metabolites, deriving from the oxidation of polyunsatured fatty acids that are released from cell membranes after cell damage or senescence of these single-celled algae. Previous results revealed harmful toxic effects of polyunsaturated aldehydes (PUAs) and hydroxyacids (HEPEs) on sea urchin Paracentrotus lividus embryonic development by testing individual compounds and mixtures of the same chemical group. Here, we investigated the combined effects of these compounds on sea urchin development at the morphological and molecular level for the first time. Our results demonstrated that oxylipin mixtures had stronger effects on sea urchin embryos compared with individual compounds, confirming that PUAs induce malformations and HEPEs cause developmental delay. This harmful effect was also confirmed by molecular analysis. Twelve new genes, involved in stress response and embryonic developmental processes, were isolated from the sea urchin P. lividus; these genes were found to be functionally interconnected with 11 genes already identified as a stress response of P. lividus embryos to single oxylipins. The expression levels of most of the analyzed genes targeted by oxylipin mixtures were involved in stress, skeletogenesis, development/differentiation, and detoxification processes. This work has important ecological implications, considering that PUAs and HEPEs represent the most abundant oxylipins in bloom-forming diatoms, opening new perspectives in understanding the molecular pathways activated by sea urchins exposed to diatom oxylipins.

Highlights

Marine organisms are continuously subjected to environmental stressors deriving from human activities [1,2,3,4], climate change [5,6,7,8,9], and toxic metabolites [10,11,12,13,14]
The only gene followed by real-time qPCR, CAT, was targeted by polyunsaturated aldehydes (PUAs) + HEPE mixture at all stages under analysis; in particular, at 5 hpf, this gene showed an increase in its expression level (2.9-fold), whereas at 21 hpf and 48 hpf it was down-regulated (2.0- and 3.0-fold, respectively). This is the first study describing the negative impact of diatom-derived PUA + HEPE mixtures on sea urchins, considered as model organisms among marine invertebrates
The negative effects of these two classes of oxylipins have been widely studied on the embryonic development of the sea urchin P. lividus

Summary

Introduction

Marine organisms are continuously subjected to environmental stressors deriving from human activities [1,2,3,4], climate change [5,6,7,8,9], and toxic metabolites [10,11,12,13,14]. Oxylipins represent a group of diverse compounds deriving from the oxidation of polyunsatured fatty acids that are released after cell damage or senescence [11,12,14] These secondary metabolites include polyunsatured aldehydes (PUAs) and other fatty acid derivatives with hydroperoxy-, hydroxy-, keto-, oxo-, and hydroxy-epoxy functionalities [11,12]. Previous studies by our group have demonstrated toxigenic effects on sea urchin P. lividus embryos exposed to individual polyunsaturated aldehydes (PUAs) and hydroxyacids (HEPEs) [30,31,32] or mixtures of these compounds belonging to the same chemical group [46,47]

Methods

Results

Conclusion