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Kim, An, Rhee, and Lim: Identification and Validation of the Relationship of the Anabolic Effect of Parathyroid Hormone with the Wnt/β-catenin Canonical Pathway
Original Article
Journal of Korean Endocrine Society

Journal of Korean Endocrine Society 2007; 22(6): 411-418.

Published online: 20 December 2007

DOI: https://doi.org/10.3803/jkes.2007.22.6.411

Identification and Validation of the Relationship of the Anabolic Effect of Parathyroid Hormone with the Wnt/β-catenin Canonical Pathway

Se Hwa Kim1, Juan Ji An2, Yumie Rhee2, 3, Sung-Kil Lim2, 3

1Department of Internal Medicine, Kwandong University College of Medicine, Korea.

2Institute of Endocrine Research, Yonsei University College of Medicine, Korea.

3Department of Internal Medicine, Yonsei University College of Medicine, Korea.

Received 3 July 2007       Accepted 22 September 2007

Copyright © 2007 Korean Endocrine Society

Abstract

Background

It has been well established that daily injections of low dose parathyroid hormone (PTH) increase bone mass in animals and humans. However, the precise mechanisms by which PTH exerts its anabolic action on bone are incompletely understood. The canonical Wnt-β-catenin signaling pathway has recently been demonstrated to have an important role in bone cell function. In the present study, we have examined the interaction between the PTH and Wnt signaling pathways in mouse osteoblastic MC3T3-E1 cells.

Methods & Results

MC3T3-E1 cells were treated with 0.01?0.84 µM recombinant PTH. β-catenin expression was significantly increased after 30 minutes of exposure to PTH and reached a maximum 2.7 fold increase at 1 hr and expression then faded at 6 hrs. In addition, treatment with PTH increased nuclear accumulation of activated β-catenin; the ratio between the nuclear to cytoplasmic protein was more than three fold at 30 minutes and beyond. Moreover, PTH stimulated T-cell factor/lymphoid enhancer factor (TCF/LEF) reporter gene activity in MC3T3-E1 cells. Confocal microscopy revealed nuclear translocation of β-catenin by PTH as compared with a glycogen synthase kinase-3β (GSK-3β) inhibitor.

Conclusion

These results suggest that the anabolic mechanism of PTH might be partially associated with the Wnt-canonical pathway. The appropriate target of another anabolic agent should be determined through further studies of this pathway.

Keywords: β-catenin, Bone, Parathyroid hormone, TCF/LEF, Wnt-canonical pathway

Figures and Tables

Fig. 1
Effect of PTH on levels of β-catenin in mouse osteoblastic cells. β-catenin expression was significantly increased after 30 minutes of exposure to PTH (10-8M) and maximized to 2.7 folds at 1 hr then faded at 6 hrs.
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Fig. 2
Effects of PTH on nuclear or cytoplasmic active β-catenin expression. PTH (10-8M) increased nuclear accumulation of activated β-catenin; the ratio between nuclear to cytoplasmic protein were more than 3 folds at 30 minutes and thereafter
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Fig. 3
Effects of PTH on intracellular translocation of β-catenin in MC3T3-E1 cells. (A) β-catenin expression (green) was weak without PTH. PTH (10-8M) treatment increases β-catenin expression in the cytoplasm as well as nuclei at 1 hr. β-catenin was mainly expressed in the nuclei after 6 hrs of PTH. LiCl (60 mM) increases β-catenin expression in the nuclei. (B) Hoechst staining of the same cells showing the nuclei (blue). (C) Confocal microscope images of the same field were taken and merged.
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Fig. 4
Effects of PTH on the TCF/LEF reporter gene activity in mouse osteoblastic cells. PTH stimulates T-cell factor/ lymphoid enhancer factor (TCF/LEF) reporter gene activity in MC3T3-E1 cells. The changes in TCF/LEF reporter gene activity are expressed as fold change over control activity (no PTH treatment).
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