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Estrogen-like effects of cadmium in vivo do not appear to be mediated via the classical estrogen receptor transcriptional pathway.

Ali I, Penttinen-Damdimopoulou PE, Mäkelä SI, Berglund M, Stenius U, Akesson A, Håkansson H, Halldin K - Environ. Health Perspect. (2010)

Bottom Line: We examined uterine weight and histology, vaginal opening, body and organ weights, Cd tissue retention, activation of mitogen-activated protein kinase (MAPK) pathways, and ERE-dependent luciferase expression.CdCl2 increased the height of the uterine luminal epithelium in a dose-dependent manner without increasing the uterine wet weight, altering the timing of vaginal opening, or affecting the luciferase activity in reproductive or nonreproductive organs.As we expected, EE2 advanced vaginal opening and increased uterine epithelial height, uterine wet weight, and luciferase activity in various tissues.

View Article: PubMed Central - PubMed

Affiliation: Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.

ABSTRACT

Background: Cadmium (Cd), a ubiquitous food contaminant, has been proposed to be an endocrine disruptor by inducing estrogenic responses in vivo. Several in vitro studies suggested that these effects are mediated via estrogen receptors (ERs).

Objective: We performed this study to clarify whether Cd-induced effects in vivo are mediated via classical ER signaling through estrogen responsive element (ERE)-regulated genes or if other signaling pathways are involved.

Methods: We investigated the estrogenic effects of cadmium chloride (CdCl2) exposure in vivo by applying the Organisation for Economic Co-operation and Development (OECD) rodent uterotrophic bioassay to transgenic ERE-luciferase reporter mice. Immature female mice were injected subcutaneously with CdCl2 (5, 50, or 500 µg/kg body weight) or with 17α-ethinylestradiol (EE2) on 3 consecutive days. We examined uterine weight and histology, vaginal opening, body and organ weights, Cd tissue retention, activation of mitogen-activated protein kinase (MAPK) pathways, and ERE-dependent luciferase expression.

Results: CdCl2 increased the height of the uterine luminal epithelium in a dose-dependent manner without increasing the uterine wet weight, altering the timing of vaginal opening, or affecting the luciferase activity in reproductive or nonreproductive organs. However, we observed changes in the phosphorylation of mouse double minute 2 oncoprotein (Mdm2) and extracellular signal-regulated kinase (Erk1/2) in the liver after CdCl2 exposure. As we expected, EE2 advanced vaginal opening and increased uterine epithelial height, uterine wet weight, and luciferase activity in various tissues.

Conclusion: Our data suggest that Cd exposure induces a limited spectrum of estrogenic responses in vivo and that, in certain targets, effects of Cd might not be mediated via classical ER signaling through ERE-regulated genes.

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Related in: MedlinePlus

Western blots and densitometric analysis of phosphorylated (p) Erk, Akt, and Mdm2 in liver homogenates after SC exposure to CdCl2, EE2, or PBS for 3 consecutive days. (A) Representative Western blots. Densitometric analysis of Mdm2(Ser166) (B), Akt(Ser473) (C), and Erk(Tyr204) (D). Data were normalized against Cdk2, and the signal for the PBS vehicle control was set to 100%. Results represent mean ± SD.*p < 0.05, **p < 0.01, and #p < 0.001, compared with PBS-treated controls by Dunnett’s multiple comparison test.
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f3-ehp-118-1389: Western blots and densitometric analysis of phosphorylated (p) Erk, Akt, and Mdm2 in liver homogenates after SC exposure to CdCl2, EE2, or PBS for 3 consecutive days. (A) Representative Western blots. Densitometric analysis of Mdm2(Ser166) (B), Akt(Ser473) (C), and Erk(Tyr204) (D). Data were normalized against Cdk2, and the signal for the PBS vehicle control was set to 100%. Results represent mean ± SD.*p < 0.05, **p < 0.01, and #p < 0.001, compared with PBS-treated controls by Dunnett’s multiple comparison test.

Mentions: Western blot analysis of liver homogenates was performed to gain knowledge on the involvement of intracellular signaling pathways. Data showed significantly increased phosphorylation of Mdm2 at Ser166 in the high-dose CdCl2-treated (500 μg/kg BW) and EE2-treated animals, whereas no changes in phosphorylation of Akt at Ser473 was observed in CdCl2- or EE2-treated groups. Phosphorylation of Erk at Tyr204 was significantly increased after exposure to 5 or 50 μg of CdCl2/kg BW compared with the PBS control (Figure 3).


Estrogen-like effects of cadmium in vivo do not appear to be mediated via the classical estrogen receptor transcriptional pathway.

Ali I, Penttinen-Damdimopoulou PE, Mäkelä SI, Berglund M, Stenius U, Akesson A, Håkansson H, Halldin K - Environ. Health Perspect. (2010)

Western blots and densitometric analysis of phosphorylated (p) Erk, Akt, and Mdm2 in liver homogenates after SC exposure to CdCl2, EE2, or PBS for 3 consecutive days. (A) Representative Western blots. Densitometric analysis of Mdm2(Ser166) (B), Akt(Ser473) (C), and Erk(Tyr204) (D). Data were normalized against Cdk2, and the signal for the PBS vehicle control was set to 100%. Results represent mean ± SD.*p < 0.05, **p < 0.01, and #p < 0.001, compared with PBS-treated controls by Dunnett’s multiple comparison test.
© Copyright Policy - public-domain
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2957917&req=5

f3-ehp-118-1389: Western blots and densitometric analysis of phosphorylated (p) Erk, Akt, and Mdm2 in liver homogenates after SC exposure to CdCl2, EE2, or PBS for 3 consecutive days. (A) Representative Western blots. Densitometric analysis of Mdm2(Ser166) (B), Akt(Ser473) (C), and Erk(Tyr204) (D). Data were normalized against Cdk2, and the signal for the PBS vehicle control was set to 100%. Results represent mean ± SD.*p < 0.05, **p < 0.01, and #p < 0.001, compared with PBS-treated controls by Dunnett’s multiple comparison test.
Mentions: Western blot analysis of liver homogenates was performed to gain knowledge on the involvement of intracellular signaling pathways. Data showed significantly increased phosphorylation of Mdm2 at Ser166 in the high-dose CdCl2-treated (500 μg/kg BW) and EE2-treated animals, whereas no changes in phosphorylation of Akt at Ser473 was observed in CdCl2- or EE2-treated groups. Phosphorylation of Erk at Tyr204 was significantly increased after exposure to 5 or 50 μg of CdCl2/kg BW compared with the PBS control (Figure 3).

Bottom Line: We examined uterine weight and histology, vaginal opening, body and organ weights, Cd tissue retention, activation of mitogen-activated protein kinase (MAPK) pathways, and ERE-dependent luciferase expression.CdCl2 increased the height of the uterine luminal epithelium in a dose-dependent manner without increasing the uterine wet weight, altering the timing of vaginal opening, or affecting the luciferase activity in reproductive or nonreproductive organs.As we expected, EE2 advanced vaginal opening and increased uterine epithelial height, uterine wet weight, and luciferase activity in various tissues.

View Article: PubMed Central - PubMed

Affiliation: Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.

ABSTRACT

Background: Cadmium (Cd), a ubiquitous food contaminant, has been proposed to be an endocrine disruptor by inducing estrogenic responses in vivo. Several in vitro studies suggested that these effects are mediated via estrogen receptors (ERs).

Objective: We performed this study to clarify whether Cd-induced effects in vivo are mediated via classical ER signaling through estrogen responsive element (ERE)-regulated genes or if other signaling pathways are involved.

Methods: We investigated the estrogenic effects of cadmium chloride (CdCl2) exposure in vivo by applying the Organisation for Economic Co-operation and Development (OECD) rodent uterotrophic bioassay to transgenic ERE-luciferase reporter mice. Immature female mice were injected subcutaneously with CdCl2 (5, 50, or 500 µg/kg body weight) or with 17α-ethinylestradiol (EE2) on 3 consecutive days. We examined uterine weight and histology, vaginal opening, body and organ weights, Cd tissue retention, activation of mitogen-activated protein kinase (MAPK) pathways, and ERE-dependent luciferase expression.

Results: CdCl2 increased the height of the uterine luminal epithelium in a dose-dependent manner without increasing the uterine wet weight, altering the timing of vaginal opening, or affecting the luciferase activity in reproductive or nonreproductive organs. However, we observed changes in the phosphorylation of mouse double minute 2 oncoprotein (Mdm2) and extracellular signal-regulated kinase (Erk1/2) in the liver after CdCl2 exposure. As we expected, EE2 advanced vaginal opening and increased uterine epithelial height, uterine wet weight, and luciferase activity in various tissues.

Conclusion: Our data suggest that Cd exposure induces a limited spectrum of estrogenic responses in vivo and that, in certain targets, effects of Cd might not be mediated via classical ER signaling through ERE-regulated genes.

Show MeSH
Related in: MedlinePlus