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

Abstract

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 (5Gy) on P. lividus analyzing by Western blotting the accumulation levels of HSP60, HSP70, BAG3 and a putative p63 at 24 and 48h after irradiation. We found an increase in the HSP70, BAG3, and p63 protein levels only 48h after irradiation, whereas no HSP60 increase was detected either at 24 or 48h. Levels of the mRNA coding for HSP70 and p63 were also investigated by relative RT-PCR and were found to increase 24h after irradiation, returning to their initial levels at 48h. Results demonstrate the presence of an adaptive regulatory mechanism operating at the transcriptional level at 24h, followed by a translational activation at 48h 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.