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Vanadate prevents glucocorticoid-induced apoptosis of osteoblasts in vitro and osteocytes in vivo

Skeletal mass is maintained by a balance between formation and resorption, cell proliferation and apoptosis. In vitro, glucocorticoids (GCs) decrease extracellular signal-regulated kinases (ERK) activation by mitogens, thus inhibiting osteoblast proliferation. Both ERK activity and proliferation are...

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Autores principales: Conradie, M M, de Wet, H, Kotze, D D R, Burrin, J M, Hough, F S, Hulley, P A
Formato: Texto
Lenguaje:English
Publicado: Society for Endocrinology 2007
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2173947/
https://www.ncbi.nlm.nih.gov/pubmed/17951534
http://dx.doi.org/10.1677/JOE-07-0217
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author Conradie, M M
de Wet, H
Kotze, D D R
Burrin, J M
Hough, F S
Hulley, P A
author_facet Conradie, M M
de Wet, H
Kotze, D D R
Burrin, J M
Hough, F S
Hulley, P A
author_sort Conradie, M M
collection PubMed
description Skeletal mass is maintained by a balance between formation and resorption, cell proliferation and apoptosis. In vitro, glucocorticoids (GCs) decrease extracellular signal-regulated kinases (ERK) activation by mitogens, thus inhibiting osteoblast proliferation. Both ERK activity and proliferation are restored by co-treatment with the protein tyrosine phosphatase inhibitor, vanadate. Since ERK signalling may also be anti-apoptotic, we explored the effects of vanadate on GC-induced apoptosis in vitro and in vivo. Apoptosis in MBA-15.4 pre-osteoblasts increased from 6 h and remained up to eightfold higher through 6 days of 10(−6) M dexamethasone (Dex) treatment. Co-incubation with 10(−7) M vanadate markedly reduced apoptosis at all time points. Vanadate also prevented GC-induced poly-ADP-ribose polymerase cleavage. We assessed the transcriptional profiles of seven anti-apoptotic proteins (Bcl-2, Bcl-X(L), inhibitors of apoptosis protein-1 (IAP-1), IAP-2, X-linked IAP (XIAP), Fas-associated death-domain-like IL-1β-converting enzyme-inhibitory protein (FLIP(Long)) and FLIP(Short)) in osteoblasts subjected to various stimuli using real-time quantitative PCR. Although these anti-apoptotic genes responded to different mitogenic conditions, Dex failed to repress their expression, and in fact significantly up-regulated Bcl-X(L), IAP-2 and XIAP. Dex may therefore induce apoptosis by up-regulating pro-apoptotic gene expression. We have previously demonstrated that rats treated with GC develop low formation osteoporosis (bone histomorphometry and DEXA) and skeletal fragility (breaking strength) that were largely prevented by co-treatment with vanadate. We report here that vertebrae from rats treated with 3·5 mg/kg per day methylprednisolone for 9 weeks showed increased incidence of terminal deoxynucleotidyl transferase-mediated biotin-dUTP nick end-labelling-positive apoptotic osteocytes, which was reduced by vanadate co-treatment. We conclude that vanadate prevents GC-induced apoptosis of pre-osteoblasts in vitro and osteocytes in vivo, and this may contribute to its bone-sparing effects in vivo.
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spelling pubmed-21739472009-01-27 Vanadate prevents glucocorticoid-induced apoptosis of osteoblasts in vitro and osteocytes in vivo Conradie, M M de Wet, H Kotze, D D R Burrin, J M Hough, F S Hulley, P A J Endocrinol Regular Papers Skeletal mass is maintained by a balance between formation and resorption, cell proliferation and apoptosis. In vitro, glucocorticoids (GCs) decrease extracellular signal-regulated kinases (ERK) activation by mitogens, thus inhibiting osteoblast proliferation. Both ERK activity and proliferation are restored by co-treatment with the protein tyrosine phosphatase inhibitor, vanadate. Since ERK signalling may also be anti-apoptotic, we explored the effects of vanadate on GC-induced apoptosis in vitro and in vivo. Apoptosis in MBA-15.4 pre-osteoblasts increased from 6 h and remained up to eightfold higher through 6 days of 10(−6) M dexamethasone (Dex) treatment. Co-incubation with 10(−7) M vanadate markedly reduced apoptosis at all time points. Vanadate also prevented GC-induced poly-ADP-ribose polymerase cleavage. We assessed the transcriptional profiles of seven anti-apoptotic proteins (Bcl-2, Bcl-X(L), inhibitors of apoptosis protein-1 (IAP-1), IAP-2, X-linked IAP (XIAP), Fas-associated death-domain-like IL-1β-converting enzyme-inhibitory protein (FLIP(Long)) and FLIP(Short)) in osteoblasts subjected to various stimuli using real-time quantitative PCR. Although these anti-apoptotic genes responded to different mitogenic conditions, Dex failed to repress their expression, and in fact significantly up-regulated Bcl-X(L), IAP-2 and XIAP. Dex may therefore induce apoptosis by up-regulating pro-apoptotic gene expression. We have previously demonstrated that rats treated with GC develop low formation osteoporosis (bone histomorphometry and DEXA) and skeletal fragility (breaking strength) that were largely prevented by co-treatment with vanadate. We report here that vertebrae from rats treated with 3·5 mg/kg per day methylprednisolone for 9 weeks showed increased incidence of terminal deoxynucleotidyl transferase-mediated biotin-dUTP nick end-labelling-positive apoptotic osteocytes, which was reduced by vanadate co-treatment. We conclude that vanadate prevents GC-induced apoptosis of pre-osteoblasts in vitro and osteocytes in vivo, and this may contribute to its bone-sparing effects in vivo. Society for Endocrinology 2007-11 /pmc/articles/PMC2173947/ /pubmed/17951534 http://dx.doi.org/10.1677/JOE-07-0217 Text en © 2007 Society for Endocrinology http://www.endocrinology.org/journals/reuselicence/ This is an Open Access article distributed under the terms of the Society for Endocrinology's Re-use Licence (http://www.endocrinology.org/journals/reuselicence/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Regular Papers
Conradie, M M
de Wet, H
Kotze, D D R
Burrin, J M
Hough, F S
Hulley, P A
Vanadate prevents glucocorticoid-induced apoptosis of osteoblasts in vitro and osteocytes in vivo
title Vanadate prevents glucocorticoid-induced apoptosis of osteoblasts in vitro and osteocytes in vivo
title_full Vanadate prevents glucocorticoid-induced apoptosis of osteoblasts in vitro and osteocytes in vivo
title_fullStr Vanadate prevents glucocorticoid-induced apoptosis of osteoblasts in vitro and osteocytes in vivo
title_full_unstemmed Vanadate prevents glucocorticoid-induced apoptosis of osteoblasts in vitro and osteocytes in vivo
title_short Vanadate prevents glucocorticoid-induced apoptosis of osteoblasts in vitro and osteocytes in vivo
title_sort vanadate prevents glucocorticoid-induced apoptosis of osteoblasts in vitro and osteocytes in vivo
topic Regular Papers
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2173947/
https://www.ncbi.nlm.nih.gov/pubmed/17951534
http://dx.doi.org/10.1677/JOE-07-0217
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