Stress response gene activation protects sea urchin embryos exposed to X-rays.

We used Paracentrotus lividus sea urchin embryos, a well-established model in developmental biology and ecotoxicology, for investigation on stress/anti-apoptotic protein expression elicited in response to harmful ionizing radiation, such as X-rays. We evaluated the acute effects of a high-dose exposure (5 Gy) on P. lividus analyzing by Western blotting the accumulation levels of HSP60, HSP70, BAG3 and a putative p63 at 24 and 48 h after irradiation. We found an increase in the HSP70, BAG3, and p63 protein levels only 48 h after irradiation, whereas no HSP60 increase was detected either at 24 or 48 h. Levels of the mRNA coding for HSP70 and p63 were also investigated by relative RT-PCR and were found to increase 24 h after irradiation, returning to their initial levels at 48 h. Results demonstrate the presence of an adaptive regulatory mechanism operating at the transcriptional level at 24 h, followed by a translational activation at 48 h post-irradiation. In conclusion, our findings confirm the sea urchin embryo as a sensible bioindicator of cell damage and we propose this model for studies on the protective pathways activated in response to X-rays. The novel result of the involvement of BAG3 and p63 in the response to X-rays, never tested so far in any other embryonic system, opens the way for their use as biomarkers of X-ray hazards.

Embryonic development and skeletogenic gene expression affected by X-rays in the Mediterranean sea urchin Paracentrotus lividus.

International concern over environmental nuclear contamination of salt water fisheries and coastal resources has attracted the interests of ecologists, marine biologists and stakeholders. There are not many studies on the effects of X-rays, a component of radionuclides emissions, on embryonic development and gene expression. The sea urchin embryo is emerging as a useful model system for environmental and eco-toxicological studies. Here, we describe how X-rays affect development and gene expression in embryos of the Mediterranean sea urchin Paracentrotus lividus. Cleavage embryos were exposed to doses from 0.1 to 5 Gy, using an Ag source of X radiation. We found a dose-dependent increase in developmental delays and severe morphological defects in embryos microscopically inspected at two endpoints, 24 and 48 h after irradiation. By analogy with classical toxicity tests parameters we defined the No Observed Effect Dose at 0.1 Gy, the Lowest Observed Effect Dose at 0.5 Gy and ED50 at 1.0 Gy. Major perturbations concerned primitive intestine and skeleton differentiation and development: X-rays exposed embryos had both no gut and arms or poorly and abnormally developed ones. We found a dose-dependent reduction in the mRNA levels of two skeleton-specific genes, Pl-SM30 (spicule matrix 30) and Pl-msp130 (matrix spicule protein 130), as measured by semi-quantitative RT-PCR and whole mount in situ hybridization, respectively. These findings indicate the sea urchin embryo as a sensible bioindicator of X-radiation and propose its use as an alternative model, emphasizing the need for further investigation aimed to protect ecosystem health.