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Calcification of Vascular Smooth Muscle Cells and Imaging of Aortic Calcification and Inflammation
08:43

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Published on: May 31, 2016

Parathyroid hormone-related protein induces G1 phase growth arrest of vascular smooth muscle cells

W D Stuart1, S Maeda, P Khera

  • 1Departments of Medicine and Molecular and Cellular Physiology, University of Cincinnati, Cincinnati, Ohio 45267, USA.

American Journal of Physiology. Endocrinology and Metabolism
|July 14, 2000
PubMed

Insights

Parathyroid hormone-related protein (PTHRP) inhibits vascular smooth muscle cell (VSMC) growth by increasing cAMP. This leads to cell cycle arrest in mid-G1, mediated by reduced cyclin D1 and increased p27(kip1).

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Parathyroid hormone-related protein (PTHRP) plays a role in cell growth regulation.
  • Vascular smooth muscle cells (VSMC) are crucial in cardiovascular function and disease.
  • Understanding cell cycle control mechanisms is vital for targeting proliferative disorders.

Purpose of the Study:

  • To elucidate the molecular mechanisms by which PTHRP inhibits VSMC proliferation.
  • To identify key proteins and pathways involved in PTHRP-induced cell cycle arrest.
  • To determine the specific phase of the cell cycle targeted by PTHRP.

Main Methods:

  • Fluorescence-activated cell sorting (FACS) analysis to assess cell cycle distribution.
  • DNA synthesis assays to measure cell proliferation.
  • Western blotting and immunoprecipitation to analyze protein expression and interactions (cyclins, CDKs, p27(kip1), Rb).

Main Results:

  • PTHRP and cAMP treatment caused VSMC accumulation in G1 phase and reduced S phase.
  • Cells became refractory to growth inhibition, indicating a mid-G1 block.
  • cAMP suppressed cyclin D1 levels without affecting cdk4, cyclin E, or cdk2.
  • PTHRP/cAMP reduced retinoblastoma protein (Rb) phosphorylation.
  • A significant increase in p27(kip1) abundance was observed, associated with cyclin D1.

Conclusions:

  • PTHRP induces VSMC cell cycle arrest in mid-G1 via increased intracellular cAMP.
  • This arrest is mediated by the suppression of cyclin D1 and induction of p27(kip1).
  • The inhibition of Rb phosphorylation is a downstream consequence of these molecular events.

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