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Bisphenol A induces otolith malformations during vertebrate embryogenesis.

Gibert Y, Sassi-Messai S, Fini JB, Bernard L, Zalko D, Cravedi JP, Balaguer P, Andersson-Lendahl M, Demeneix B, Laudet V - BMC Dev. Biol. (2011)

Bottom Line: Here, we investigated BPA effects during embryonic development using the zebrafish and Xenopus models.As no effects on otolith development were seen with exposure to micromolar concentrations of thyroid hormone, 17-ß-estradiol or of the estrogen receptor antagonist ICI 182,780 we conclude that the effects of BPA are independent of estrogen receptors or thyroid-hormone receptors.The data suggest that the spectrum of BPA action is wider than previously expected and argue for a systematic survey of the developmental effects of this endocrine disruptor.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut de Génomique Fonctionnelle de Lyon; Université de Lyon; Université Lyon 1; CNRS; INRA; Ecole Normale Supérieure de Lyon; 46 allée d'Italie, 69364 Lyon Cedex 07, France. vincent.laudet@ens-lyon.fr

ABSTRACT

Background: The plastic monomer and plasticizer bisphenol A (BPA), used for manufacturing polycarbonate plastic and epoxy resins, is produced at over 2.5 million metric tons per year. Concerns have been raised that BPA acts as an endocrine disruptor on both developmental and reproductive processes and a large body of evidence suggests that BPA interferes with estrogen and thyroid hormone signaling. Here, we investigated BPA effects during embryonic development using the zebrafish and Xenopus models.

Results: We report that BPA exposure leads to severe malformations of the otic vesicle. In zebrafish and in Xenopus embryos, exposure to BPA during the first developmental day resulted in dose-dependent defects in otolith formation. Defects included aggregation, multiplication and occasionally failure to form otoliths. As no effects on otolith development were seen with exposure to micromolar concentrations of thyroid hormone, 17-ß-estradiol or of the estrogen receptor antagonist ICI 182,780 we conclude that the effects of BPA are independent of estrogen receptors or thyroid-hormone receptors. Na+/K+ ATPases are crucial for otolith formation in zebrafish. Pharmacological inhibition of the major Na+/K+ ATPase with ouabain can rescue the BPA-induced otolith phenotype.

Conclusions: The data suggest that the spectrum of BPA action is wider than previously expected and argue for a systematic survey of the developmental effects of this endocrine disruptor.

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Related in: MedlinePlus

BPA treatment induces otolith abnormalities. A: BPA induced otolith malformation is dose dependent. Embryos were treated with different concentrations of BPA from 5 hpf onwards. Black bars represent embryos showing no otolith abnormalities, red bars represent treated embryos showing otolith abnormalities. (*: P < 0.01, Fisher test after Bonferroni correction). B: Anterior otolith (ao, upper left) and posterior otolith (po, upper middle) of control embryo and ao (lower left) and po (lower middle) of embryos treated with 70 μM BPA from 5 to 50 hpf showing otolith aggregation. In some rare cases a single otolith (upper right) or extra otolith (eo lower right) are observed. C: Upper panel: control embryo at 50 hpf (Upper right: close up of the otic vesicle). Lower panel: overall shape of BPA treated embryos form 6-50 hpf resembles control embryos, but display otolith aggregates (arrow). Lower right: close up of the otic vesicle in a BPA treated embryo form 24-50 hpf showing normal otoliths. D: After 75 hours of exposure, the concentration of BPA measured in embryos is 0.7 μg equivalent per mg fresh weight and 0.22 μg of BPF equivalent per mg fresh weight; see also Figure 2 C-E. E: BPA induces malformation of the otic vesicle in Xenopus embryos. Xenopus embryos were exposed to BPA (5 or 10 μM) from stage NF 18 to stage NF 40 (48 h) and examined at stage NF 45. The upper panel shows the morphology of the otoliths (or otoconia [73]) in control and BPA treated embryos. Note that 5 and 10 μM of BPA induce a progressive reduction in the size of the otoconia. The lower panel shows the semi-circular canals with a reduction in the distance between the two semi circular canals (arrowheads) induced by BPA. Similarly, the morphology of the developing semi circular canals is flattened under BPA treatment.
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Figure 1: BPA treatment induces otolith abnormalities. A: BPA induced otolith malformation is dose dependent. Embryos were treated with different concentrations of BPA from 5 hpf onwards. Black bars represent embryos showing no otolith abnormalities, red bars represent treated embryos showing otolith abnormalities. (*: P < 0.01, Fisher test after Bonferroni correction). B: Anterior otolith (ao, upper left) and posterior otolith (po, upper middle) of control embryo and ao (lower left) and po (lower middle) of embryos treated with 70 μM BPA from 5 to 50 hpf showing otolith aggregation. In some rare cases a single otolith (upper right) or extra otolith (eo lower right) are observed. C: Upper panel: control embryo at 50 hpf (Upper right: close up of the otic vesicle). Lower panel: overall shape of BPA treated embryos form 6-50 hpf resembles control embryos, but display otolith aggregates (arrow). Lower right: close up of the otic vesicle in a BPA treated embryo form 24-50 hpf showing normal otoliths. D: After 75 hours of exposure, the concentration of BPA measured in embryos is 0.7 μg equivalent per mg fresh weight and 0.22 μg of BPF equivalent per mg fresh weight; see also Figure 2 C-E. E: BPA induces malformation of the otic vesicle in Xenopus embryos. Xenopus embryos were exposed to BPA (5 or 10 μM) from stage NF 18 to stage NF 40 (48 h) and examined at stage NF 45. The upper panel shows the morphology of the otoliths (or otoconia [73]) in control and BPA treated embryos. Note that 5 and 10 μM of BPA induce a progressive reduction in the size of the otoconia. The lower panel shows the semi-circular canals with a reduction in the distance between the two semi circular canals (arrowheads) induced by BPA. Similarly, the morphology of the developing semi circular canals is flattened under BPA treatment.

Mentions: Zebrafish embryos were treated from 5 hours post-fertilization (hpf) onwards with concentrations of BPA ranging from 0.01 μM to 100 μM. While exposure to BPA <5 μM did not induced phenotypic abnormalities, treatment with higher doses induced otolith malformations (Figure 1A). These effects were seen in a small proportion (<5%) of embryos at 5 μM and increased at higher doses with more than 50% of affected embryos at 25 μM BPA. Notably, 100 μM BPA induced embryonic mortality probably linked to cardiac edema and cessation of blood flow. Abnormalities included aggregation of the otoliths, appearance of extra otoliths or their absence (Figure 1B). The vast majority of embryos exhibit bilateral aggregation of both anterior and posterior otoliths (< 18 otoliths forming an aggregate in the posterior otolith, Figure 1B). In some cases, altered semi-circular canals development was observed, but as this effect was highly variable it was not further characterized. In addition we observed that BPA had a mild effect on decreasing the general embryo pigmentation (not shown).


Bisphenol A induces otolith malformations during vertebrate embryogenesis.

Gibert Y, Sassi-Messai S, Fini JB, Bernard L, Zalko D, Cravedi JP, Balaguer P, Andersson-Lendahl M, Demeneix B, Laudet V - BMC Dev. Biol. (2011)

BPA treatment induces otolith abnormalities. A: BPA induced otolith malformation is dose dependent. Embryos were treated with different concentrations of BPA from 5 hpf onwards. Black bars represent embryos showing no otolith abnormalities, red bars represent treated embryos showing otolith abnormalities. (*: P < 0.01, Fisher test after Bonferroni correction). B: Anterior otolith (ao, upper left) and posterior otolith (po, upper middle) of control embryo and ao (lower left) and po (lower middle) of embryos treated with 70 μM BPA from 5 to 50 hpf showing otolith aggregation. In some rare cases a single otolith (upper right) or extra otolith (eo lower right) are observed. C: Upper panel: control embryo at 50 hpf (Upper right: close up of the otic vesicle). Lower panel: overall shape of BPA treated embryos form 6-50 hpf resembles control embryos, but display otolith aggregates (arrow). Lower right: close up of the otic vesicle in a BPA treated embryo form 24-50 hpf showing normal otoliths. D: After 75 hours of exposure, the concentration of BPA measured in embryos is 0.7 μg equivalent per mg fresh weight and 0.22 μg of BPF equivalent per mg fresh weight; see also Figure 2 C-E. E: BPA induces malformation of the otic vesicle in Xenopus embryos. Xenopus embryos were exposed to BPA (5 or 10 μM) from stage NF 18 to stage NF 40 (48 h) and examined at stage NF 45. The upper panel shows the morphology of the otoliths (or otoconia [73]) in control and BPA treated embryos. Note that 5 and 10 μM of BPA induce a progressive reduction in the size of the otoconia. The lower panel shows the semi-circular canals with a reduction in the distance between the two semi circular canals (arrowheads) induced by BPA. Similarly, the morphology of the developing semi circular canals is flattened under BPA treatment.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3040707&req=5

Figure 1: BPA treatment induces otolith abnormalities. A: BPA induced otolith malformation is dose dependent. Embryos were treated with different concentrations of BPA from 5 hpf onwards. Black bars represent embryos showing no otolith abnormalities, red bars represent treated embryos showing otolith abnormalities. (*: P < 0.01, Fisher test after Bonferroni correction). B: Anterior otolith (ao, upper left) and posterior otolith (po, upper middle) of control embryo and ao (lower left) and po (lower middle) of embryos treated with 70 μM BPA from 5 to 50 hpf showing otolith aggregation. In some rare cases a single otolith (upper right) or extra otolith (eo lower right) are observed. C: Upper panel: control embryo at 50 hpf (Upper right: close up of the otic vesicle). Lower panel: overall shape of BPA treated embryos form 6-50 hpf resembles control embryos, but display otolith aggregates (arrow). Lower right: close up of the otic vesicle in a BPA treated embryo form 24-50 hpf showing normal otoliths. D: After 75 hours of exposure, the concentration of BPA measured in embryos is 0.7 μg equivalent per mg fresh weight and 0.22 μg of BPF equivalent per mg fresh weight; see also Figure 2 C-E. E: BPA induces malformation of the otic vesicle in Xenopus embryos. Xenopus embryos were exposed to BPA (5 or 10 μM) from stage NF 18 to stage NF 40 (48 h) and examined at stage NF 45. The upper panel shows the morphology of the otoliths (or otoconia [73]) in control and BPA treated embryos. Note that 5 and 10 μM of BPA induce a progressive reduction in the size of the otoconia. The lower panel shows the semi-circular canals with a reduction in the distance between the two semi circular canals (arrowheads) induced by BPA. Similarly, the morphology of the developing semi circular canals is flattened under BPA treatment.
Mentions: Zebrafish embryos were treated from 5 hours post-fertilization (hpf) onwards with concentrations of BPA ranging from 0.01 μM to 100 μM. While exposure to BPA <5 μM did not induced phenotypic abnormalities, treatment with higher doses induced otolith malformations (Figure 1A). These effects were seen in a small proportion (<5%) of embryos at 5 μM and increased at higher doses with more than 50% of affected embryos at 25 μM BPA. Notably, 100 μM BPA induced embryonic mortality probably linked to cardiac edema and cessation of blood flow. Abnormalities included aggregation of the otoliths, appearance of extra otoliths or their absence (Figure 1B). The vast majority of embryos exhibit bilateral aggregation of both anterior and posterior otoliths (< 18 otoliths forming an aggregate in the posterior otolith, Figure 1B). In some cases, altered semi-circular canals development was observed, but as this effect was highly variable it was not further characterized. In addition we observed that BPA had a mild effect on decreasing the general embryo pigmentation (not shown).

Bottom Line: Here, we investigated BPA effects during embryonic development using the zebrafish and Xenopus models.As no effects on otolith development were seen with exposure to micromolar concentrations of thyroid hormone, 17-ß-estradiol or of the estrogen receptor antagonist ICI 182,780 we conclude that the effects of BPA are independent of estrogen receptors or thyroid-hormone receptors.The data suggest that the spectrum of BPA action is wider than previously expected and argue for a systematic survey of the developmental effects of this endocrine disruptor.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut de Génomique Fonctionnelle de Lyon; Université de Lyon; Université Lyon 1; CNRS; INRA; Ecole Normale Supérieure de Lyon; 46 allée d'Italie, 69364 Lyon Cedex 07, France. vincent.laudet@ens-lyon.fr

ABSTRACT

Background: The plastic monomer and plasticizer bisphenol A (BPA), used for manufacturing polycarbonate plastic and epoxy resins, is produced at over 2.5 million metric tons per year. Concerns have been raised that BPA acts as an endocrine disruptor on both developmental and reproductive processes and a large body of evidence suggests that BPA interferes with estrogen and thyroid hormone signaling. Here, we investigated BPA effects during embryonic development using the zebrafish and Xenopus models.

Results: We report that BPA exposure leads to severe malformations of the otic vesicle. In zebrafish and in Xenopus embryos, exposure to BPA during the first developmental day resulted in dose-dependent defects in otolith formation. Defects included aggregation, multiplication and occasionally failure to form otoliths. As no effects on otolith development were seen with exposure to micromolar concentrations of thyroid hormone, 17-ß-estradiol or of the estrogen receptor antagonist ICI 182,780 we conclude that the effects of BPA are independent of estrogen receptors or thyroid-hormone receptors. Na+/K+ ATPases are crucial for otolith formation in zebrafish. Pharmacological inhibition of the major Na+/K+ ATPase with ouabain can rescue the BPA-induced otolith phenotype.

Conclusions: The data suggest that the spectrum of BPA action is wider than previously expected and argue for a systematic survey of the developmental effects of this endocrine disruptor.

Show MeSH
Related in: MedlinePlus