The role of dopamine and serotonin in regulating bone mass and strength: Studies on dopamine and serotonin transporter null mice

M. Bliziotes, M. Gunness, A. Eshleman, Kristine Wiren

Research output: Contribution to journalArticle

49 Citations (Scopus)

Abstract

Neurotransmitter regulation of bone metabolism has been a subject of increasing interest and investigation. Dopamine (DA) has been reported to have effects on calcium and phosphorus metabolism. The dopamine transporter (DAT) is believed to control the temporal and spatial activity of released DA by rapid uptake of the neurotransmitter into presynaptic terminals. We have evaluated the histologic and biomechanical properties of the skeleton in mice homozygous for deletion of the DA transporter gene (DAT -/-) to help delineate the role of DA in bone biology. We have demonstrated that DAT -/- mice have reduced bone mass and strength. DAT -/- animals have shorter femur length and dry weight, and lower ash calcium content. Cancellous bone volume in the DAT -/- proximal tibial metaphysis is significantly decreased with reduced trabecular thickness. DAT -/- vertebrae have lower cancellous bone volume as a consequence of increased trabecular spacing and reduced trabecular number, and cortical thickness and bone area in the femoral diaphysis are reduced. The ultimate bending load (femoral strength) for the DAT -/- mice is 30% lower than the wild-type mice. Thus, deletion of the DAT gene results in deficiencies in skeletal structure and integrity. Since serotonin (5-HT) plays a role as a regulator of craniofacial morphogenesis, we explored the expression and function of 5-HT receptors and the 5-HT transporter (5-HTT) in bone. Primary cultures of rat osteoblasts (rOB) and a variety of clonal osteoblastic cell lines including ROS 17/2.8, UMR 106-H5 and Py1a show mRNA expression for the 5-HTT, and the 5-HT1A, 5-HT1D, 5-HT2A and 5-HT2B receptors by RT-PCR analysis and immunoblot. A relatively high density of nanomolar affinity 5-HTT binding sites is present in ROS 17/2.8 and UMR 106-H5 cells. The maximal [3H]5-HT uptake rate in ROS cells was 110 pmol/10 min/well, with a Km value of 1.13 μM. In normal differentiating rOB cultures, 5-HTT functional activity was observed initially at day 25, and activity increased by almost eight-fold at day 31. In mature rOB cultures, the estimated density of [125I]RTI-55 binding sites was 600 fmol/mg protein. PMA treatment caused a significant 40% reduction in the maximal uptake rate of [3H]5-HT, an effect prevented by pretreatment with staurosporine. 5-HT potentiates the PTH-induced increase in AP-1 activity in UMR 106-H5 cells. In 5-HTT -/- animals, cancellous bone volume (BV/TV) in the lumbar vertebrae is reduced, with a trend toward decreased trabecular thickness and trabecular number. These results demonstrate that osteoblastic cells express a functional serotonin system, with mechanisms for responding to and regulating uptake of 5-HT, and disruption of the 5-HTT gene may cause osteopenia.

Original languageEnglish (US)
Pages (from-to)291-295
Number of pages5
JournalJournal of Musculoskeletal Neuronal Interactions
Volume2
Issue number3
StatePublished - 2002

Fingerprint

Serotonin Plasma Membrane Transport Proteins
Dopamine Plasma Membrane Transport Proteins
Dopamine
Serotonin
Bone and Bones
Osteoblasts
Thigh
Neurotransmitter Agents
Receptor, Serotonin, 5-HT2B
Binding Sites
Genes
Calcium
Diaphyses
Lumbar Vertebrae
Staurosporine
Metabolic Bone Diseases
Serotonin Receptors
Transcription Factor AP-1
Presynaptic Terminals
Morphogenesis

Keywords

  • Bone
  • Dopamine
  • Neurotransmitter
  • Osteoblast
  • Serotonin

ASJC Scopus subject areas

  • Neuroscience(all)
  • Endocrinology

Cite this

The role of dopamine and serotonin in regulating bone mass and strength : Studies on dopamine and serotonin transporter null mice. / Bliziotes, M.; Gunness, M.; Eshleman, A.; Wiren, Kristine.

In: Journal of Musculoskeletal Neuronal Interactions, Vol. 2, No. 3, 2002, p. 291-295.

Research output: Contribution to journalArticle

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KW - Serotonin

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