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Effect of bisphenol A (BPA) on urchin embryo genes expression and ultrastructure

Global usage of bisphenol A (BPA) in production of polycarbonate plastic resulted with its high concentrations distributed and accumulated in the environment. It causes numerous negative effects and one the most known is in induction of endocrine disruption. Due to authorized discharges of treated industrial waste waters, BPA is ubiquitously present and more persistent in water environments where it leads to reasonable concern over potential impact on aquatic biota. Our research focused on study of toxic effects of environment-relevant concentrations of BPA (100 nM and 4 µM) on embryonic development (2-cell, pluteus) of the rocky sea urchin (Paracentrotus lividus). We examined the extent of the role of multidrug efflux transport, potentially involved in the expelling of intercellulary-accumulated BPA, as well as the mechanism and level of cytotoxic effects on embryo development. Results of functional calcein-AM assay, intracellular BPA accumulation and real time quantitative PCR (qPCR) measurements clearly indicate the importance of P- glycoprotein (ABCB1) as the role member of multixenobiotic resistance mechanism (MXR) in defense against BPA. Moreover, qPCR results indicate that BPA is inducing the synthesis of orphan steroid hormone receptor 2 (SHR2), a nuclear receptor known to bind estradiol in sea urchin embryos. SHR2 prominent position in the activation of transcriptional factors necessary during the early development and cells harmonization suggests that BPA in urchin embryo interferes in the development as an endocrine disruptor. Cytotoxic effects of BPA included the impairment of embryo first cell division, validated by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and immunohistochemistry (IHC) methods. These results suggest that BPA is causing disorder in karyokinesis inducing formation of polykarya in 2- cell embryos that consequently leading to aneuploydia, and retardation of embryo development and mortality. It is still unclear if developmental impairment in BPA-exposed embryos is related to the indirect impairment of MXR activation through actin dysfunction, or to general errors in cytoskeletal functioning in cell cycle, or both.

Bisphenol A; Multidrug efflux transport; Electron microscopy; Fluorescence; Gene expression; HPLC; Imunohistochemistry; Sea urchin embryo

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