Combined Effects of Cadmium and UVB Radiation on Sea Urchin Embryos: Skeleton Impairment Parallels p38 MAPK Activation and Stress Genes Overexpression

Abstract

Human and natural activities release many pollutants in the marine environment. The mixture of pollutants can affect many organisms concurrently. We used Paracentrotus lividus as a model to analyze the effects on signal transduction pathways and stress gene expression in embryos exposed continuously to double stress, i.e., cadmium (Cd) from fertilization and UVB at cleavage (Cd/UVB-embryos). By microscopical inspection, we evaluated embryonic morphology after 72 h of development. Tissue-specific markers were used to assess mesoderm differentiation by immunofluorescence. We analyzed p38MAPK, ERK1/2, and JNK activation by Western blot and mRNA profiles of Pl-MT, Pl-14-3-3epsilon, and Pl-jun genes by real-time quantitative polymerase chain reaction (qPCR) and the localization of their transcripts by whole mount in situ hybridization (WMISH). We found that the Cd/UVB combined exposure induced morphological malformations in 76% of pluteus embryos, mainly affecting the development of the skeleton, including the normal branching of skeletal roads. In Cd/UVB-embryos, p38MAPK was activated 1 h after UVB exposure and a remarkable overexpression of the Pl-MT, Pl-14.3.3epsilon, and Pl-jun genes 24 h after UVB exposure. Pl-MT and Pl-14.3.3epsilon mRNAs were misexpressed as they were localized in a position different from that observed in wild-type embryos, i.e., the intestine. On the contrary, Pl-jun mRNA has remained localized in the skeletogenic cells despite their displacement in exposed embryos. In conclusion, Cd/UVB exposure affected skeletal patterning producing alternative morphologies in which p38MAPK activation and Pl-MT, Pl-14.3.3epsilon, and Pl-jun gene overexpression seem linked to a protective role against the stress response induced by Cd/UVB.

Subtle reproductive impairment through nitric oxide-mediated mechanisms in sea urchins from an area affected by harmful algal blooms

“…cDNA diluted 1:5 with H 2 O was used in Real Time qPCR experiments as described previously 24 . The data were normalized for the reference gene PlZ12-1 , which resulted to be the most suitable reference gene in previous studies 24 25 56 57 58 59 60 .…”

Effects of exposure to gadolinium on the development of geographically and phylogenetically distant sea urchins species

“…The sea urchin embryo has long been an important model organism in developmental biology and eco-toxicology to assess the hazard posed by contaminants entering the marine environment (Radenac et al, 2001;Russo et al, 2003;Roccheri et al, 2004;Pinsino et al, 2010;Tellis et al, 2014). A wealth of research with sea urchin embryos and larvae have shown that chemical pollutants impair development and that the larval skeleton is a particularly vulnerable response variable for ecotoxicological tests (Bonaventura et al, 2015;Morroni et al, 2016). For instance, exposure to toxic elements (e.g.…”

Gene Expression Analysis of the Stress Response to Lithium, Nickel, and Zinc in Paracentrotus lividus Embryos

“…The two fox genes analyzed are differently expressed in late sea urchin embryos, i.e., foxO is expressed in PMCs, suggesting its involvement in biomineralization, whereas foxG expression is restricted to the ciliated band, suggesting an involvement in nervous processes [71]. By our KO analysis, p38MAPK gene enriched the FoxO signaling pathway, even though this gene is known to have a dual role in sea urchin, i.e., an essential regulator of embryonic development, involved in D/V axis specification and skeletogenesis [72], and a stress marker [73].…”