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Gewählte Publikation:

Publikationstyp: Zeitschriftenaufsatz
Dokumenttyp: Originalarbeit

Jahr: 2012

AutorInnen: Schneider, MR; Dahlhoff, M; Andrukhova, O; Grill, J; Glösmann, M; Schüler, C; Weber, K; Wolf, E; Erben, RG

Titel: Normal epidermal growth factor receptor signaling is dispensable for bone anabolic effects of parathyroid hormone.

Quelle: Bone. 2012; 50(1):237-244



Autor/innen der Vetmeduni Vienna:

Andrukhova Olena
Erben Reinhold
Glösmann Martin
Schüler Christiane

Beteiligte Vetmed-Organisationseinheiten
Institut für Physiologie, Pathophysiologie und Biophysik, Abteilung für Physiologie, Pathophysiologie und experimentelle Endokrinologie


Abstract:
Although the bone anabolic properties of intermittent parathyroid hormone (PTH) have long been employed in the treatment of osteoporosis, the molecular mechanisms behind this action remain largely unknown. Previous studies showed that PTH increases the expression and the activity of epidermal growth factor receptor (EGFR) in osteoblasts, and activation of ERK1/2 by PTH in osteoblasts was demonstrated to induce the proteolytical release of EGFR ligands and EGFR transactivation. However, conclusive evidence for an important role of the EGFR system in mediating the anabolic actions of intermittent PTH on bone in vivo is lacking. Here, we evaluated the effects of intermittent PTH on bone in Waved-5 (Wa5) mice which carry an antimorphic Egfr allele whose product acts as a dominant negative receptor. Heterozygous Wa5 females and control littermates received a subcutaneous injection of PTH (80 μg/kg) or buffer on 5 days per week for 4 weeks. Wa5 mice had slightly lower total bone mineral density (BMD), but normal cancellous bone volume and turnover in the distal femoral metaphysis. The presence of the antimorphic Egfr allele neither influenced the PTH-induced increase in serum osteocalcin nor the increases in distal femoral BMD, cortical thickness, cancellous bone volume, and cancellous bone formation rate. Similarly, the PTH-induced rise in lumbar vertebral BMD was unchanged in Wa5 relative to wild-type mice. Wa5-derived osteoblasts showed considerably lower basal extracellular signal-regulated kinase 1/2 (ERK1/2) activation as compared to control osteoblasts. Whereas activation of ERK1/2 by the EGFR ligand amphiregulin was largely blocked in Wa5 osteoblasts, treatment with PTH induced ERK1/2 activation comparable to that observed in control osteoblasts, relative to baseline levels. Our data indicate that impairment of EGFR signaling does not affect the anabolic action of intermittent PTH on cancellous and cortical bone.

Keywords Pubmed: Anabolic Agents/pharmacology*
Animals
Bone Density/drug effects
Bone and Bones/drug effects*
Bone and Bones/metabolism*
Bone and Bones/ultrastructure
Female
Mice
Mice, Transgenic
Osteoblasts/cytology
Osteoblasts/drug effects
Osteoblasts/metabolism
Osteocalcin/blood
Parathyroid Hormone/pharmacology*
Receptor, Epidermal Growth Factor/genetics
Receptor, Epidermal Growth Factor/metabolism*
Signal Transduction/physiology*
X-Ray Microtomography


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