Limits...
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.

Show MeSH

Related in: MedlinePlus

Chemical inhibition of Na/K ATPase rescues the BPA induced phenotype. (A) 50 hpf control embryo with two normal otolith. (B) Treatment with 1.8 mM ouabain from 6 hpf onwards leads to one misformed otolith. (C) Embryo treated with 70 μM BPA from 5 hpf onwards leads to otolith aggregates. (D) Co treatment with 70 μM BPA and 1.8 mM oubain from 6 hpf onwards leads to normal otolith. (E) Co treatment with 70 μM BPA and 0.9 mM oubain from 6 hpf onwards leads to a mild BPA like phenotype. In some cases one almost normal otolith is found (arrow). (F) Co treatment with 50 μM BPA and 1.8 mM oubain from 6 hpf onwards leads to two normal otoliths. (G)α1a1 morphants display a complete absence of otolith. (H) 70 μM BPA of α1a1 morphants did not rescue otolith formation and result in a complete absence of otolith. (I)α1a1 is expressed in the lower membrane of the otic vesicle at 24 hpf. (J) A similar expression of α1a1 is detected in BPA treated embryos.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3040707&req=5

Figure 6: Chemical inhibition of Na/K ATPase rescues the BPA induced phenotype. (A) 50 hpf control embryo with two normal otolith. (B) Treatment with 1.8 mM ouabain from 6 hpf onwards leads to one misformed otolith. (C) Embryo treated with 70 μM BPA from 5 hpf onwards leads to otolith aggregates. (D) Co treatment with 70 μM BPA and 1.8 mM oubain from 6 hpf onwards leads to normal otolith. (E) Co treatment with 70 μM BPA and 0.9 mM oubain from 6 hpf onwards leads to a mild BPA like phenotype. In some cases one almost normal otolith is found (arrow). (F) Co treatment with 50 μM BPA and 1.8 mM oubain from 6 hpf onwards leads to two normal otoliths. (G)α1a1 morphants display a complete absence of otolith. (H) 70 μM BPA of α1a1 morphants did not rescue otolith formation and result in a complete absence of otolith. (I)α1a1 is expressed in the lower membrane of the otic vesicle at 24 hpf. (J) A similar expression of α1a1 is detected in BPA treated embryos.

Mentions: One of the main enzymes involved in ion exchange and various aspects of inner ear formation are the ouabain sensitive Na+/K+ ATPases [54,66]. Addition of ouabain to embryos was used to examine whether the effects of BPA implicated Na+/K+ ATPases. Ouabain exposure (1.8 mM from 6 hpf onwards) caused aberrant development of otoliths, with either complete absence (20% of the embryos) or one misformed otolith (80%; see Figure 6B). Higher doses led to embryonic mortality at 48 hpf as reported by Blasiole et al. [54]. This phenotype could be viewed as opposite to that caused by BPA (at 70 μM from 6 hpf onwards) i.e. formation of multiple small aggregated otoliths (Figure 6C). Interestingly when we co-treated embryos with 1.8 mM ouabain + 70 μM BPA a normal otolith formation was observed (Figure 6D): two otoliths are present in these fish. We interpret this as a rescue of the BPA effect by ouabain treatment. This suggests that the two compounds have opposite effects: on the one hand, BPA promotes multiplication and aggregation of otoliths, whereas, inversely, ouabain blocks their formation. We thus explored the dose-dependency of this effect. Using a lower dose of ouabain (0.9 mM, half dose) induced only very limited rescue of the full dose BPA phenotype. However, with this half dose ouabain and full dose BPA embryos were less severely affected than the full dose BPA alone (Compare Figures 6C and 6E). In contrast, full dose ouabain plus lower dose BPA (50 μM) treated embryos also displayed normal otoliths, with two distinct otoliths while only one misshapen otolith resulted from full dose ouabain alone (Compare Figures 6F and 6B).


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)

Chemical inhibition of Na/K ATPase rescues the BPA induced phenotype. (A) 50 hpf control embryo with two normal otolith. (B) Treatment with 1.8 mM ouabain from 6 hpf onwards leads to one misformed otolith. (C) Embryo treated with 70 μM BPA from 5 hpf onwards leads to otolith aggregates. (D) Co treatment with 70 μM BPA and 1.8 mM oubain from 6 hpf onwards leads to normal otolith. (E) Co treatment with 70 μM BPA and 0.9 mM oubain from 6 hpf onwards leads to a mild BPA like phenotype. In some cases one almost normal otolith is found (arrow). (F) Co treatment with 50 μM BPA and 1.8 mM oubain from 6 hpf onwards leads to two normal otoliths. (G)α1a1 morphants display a complete absence of otolith. (H) 70 μM BPA of α1a1 morphants did not rescue otolith formation and result in a complete absence of otolith. (I)α1a1 is expressed in the lower membrane of the otic vesicle at 24 hpf. (J) A similar expression of α1a1 is detected in BPA treated embryos.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 6: Chemical inhibition of Na/K ATPase rescues the BPA induced phenotype. (A) 50 hpf control embryo with two normal otolith. (B) Treatment with 1.8 mM ouabain from 6 hpf onwards leads to one misformed otolith. (C) Embryo treated with 70 μM BPA from 5 hpf onwards leads to otolith aggregates. (D) Co treatment with 70 μM BPA and 1.8 mM oubain from 6 hpf onwards leads to normal otolith. (E) Co treatment with 70 μM BPA and 0.9 mM oubain from 6 hpf onwards leads to a mild BPA like phenotype. In some cases one almost normal otolith is found (arrow). (F) Co treatment with 50 μM BPA and 1.8 mM oubain from 6 hpf onwards leads to two normal otoliths. (G)α1a1 morphants display a complete absence of otolith. (H) 70 μM BPA of α1a1 morphants did not rescue otolith formation and result in a complete absence of otolith. (I)α1a1 is expressed in the lower membrane of the otic vesicle at 24 hpf. (J) A similar expression of α1a1 is detected in BPA treated embryos.
Mentions: One of the main enzymes involved in ion exchange and various aspects of inner ear formation are the ouabain sensitive Na+/K+ ATPases [54,66]. Addition of ouabain to embryos was used to examine whether the effects of BPA implicated Na+/K+ ATPases. Ouabain exposure (1.8 mM from 6 hpf onwards) caused aberrant development of otoliths, with either complete absence (20% of the embryos) or one misformed otolith (80%; see Figure 6B). Higher doses led to embryonic mortality at 48 hpf as reported by Blasiole et al. [54]. This phenotype could be viewed as opposite to that caused by BPA (at 70 μM from 6 hpf onwards) i.e. formation of multiple small aggregated otoliths (Figure 6C). Interestingly when we co-treated embryos with 1.8 mM ouabain + 70 μM BPA a normal otolith formation was observed (Figure 6D): two otoliths are present in these fish. We interpret this as a rescue of the BPA effect by ouabain treatment. This suggests that the two compounds have opposite effects: on the one hand, BPA promotes multiplication and aggregation of otoliths, whereas, inversely, ouabain blocks their formation. We thus explored the dose-dependency of this effect. Using a lower dose of ouabain (0.9 mM, half dose) induced only very limited rescue of the full dose BPA phenotype. However, with this half dose ouabain and full dose BPA embryos were less severely affected than the full dose BPA alone (Compare Figures 6C and 6E). In contrast, full dose ouabain plus lower dose BPA (50 μM) treated embryos also displayed normal otoliths, with two distinct otoliths while only one misshapen otolith resulted from full dose ouabain alone (Compare Figures 6F and 6B).

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