Thymidine phosphorylase inhibits vascular smooth muscle cell proliferation via upregulation of STAT3

Biochim Biophys Acta. 2012 Aug;1823(8):1316-23. doi: 10.1016/j.bbamcr.2012.05.025. Epub 2012 Jun 2.

Abstract

Dysregulated growth and motility of vascular smooth muscle cells (VSMC) play important role in obstructive vascular diseases. We previously reported that gene transfer of thymidine phosphorylase (TP) into rat VSMC inhibits cell proliferation and attenuates balloon injury induced neointimal hyperplasia; however, the mechanism remains unclear. The current study identified a signaling pathway that mediates effect of TP inhibited VSMC proliferation with a TP activity-dependent manner. Rat VSMC overexpressing human TP gene (C2) or control empty vector (PC) were used. Serum stimulation induced constitutive STAT3 phosphorylation at tyrosine705 in C2 cell but not in PC, which was independent of JAK2 signaling pathway. Inhibition of Src family kinases activity inhibited STAT3 phosphorylation in C2 cells. Lyn activity was higher in C2 cell than in PC. SiRNA based gene knockdown of Lyn significantly decreased serum induced STAT3 phosphorylation in C2 and dramatically increased proliferation of this cell, suggesting that Lyn plays a pivotal role in TP inhibited VSMC proliferation. Unphosphorylated STAT3 (U-STAT3) expression was significantly increased in C2 cells, which may be due to the increased STAT3 transcription. Gene transfection of mouse wild-type or Y705F mutant STAT3 into PC cell or mouse primary cultured VSMC significantly reduced proliferation of these cells, suggesting that overexpression of U-STAT3 inhibits VSMC proliferation. We conclude that Lyn mediates TP induced STAT3 activation, which subsequently contributes to upregulate expression of U-STAT3. The U-STAT3 plays a critical role in inhibiting VSMC proliferation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Proliferation*
  • Cells, Cultured
  • Humans
  • Janus Kinase 2 / metabolism
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Muscle, Smooth, Vascular / cytology*
  • Myocytes, Smooth Muscle / enzymology
  • Myocytes, Smooth Muscle / physiology*
  • Phosphorylation
  • Protein Processing, Post-Translational
  • Rats, Sprague-Dawley
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / genetics
  • STAT3 Transcription Factor / genetics*
  • STAT3 Transcription Factor / metabolism
  • Thymidine Phosphorylase / biosynthesis
  • Thymidine Phosphorylase / genetics
  • Thymidine Phosphorylase / physiology*
  • Up-Regulation
  • src-Family Kinases / metabolism

Substances

  • Recombinant Proteins
  • STAT3 Transcription Factor
  • Stat3 protein, rat
  • TYMP protein, human
  • Thymidine Phosphorylase
  • Jak2 protein, rat
  • Janus Kinase 2
  • lyn protein-tyrosine kinase
  • src-Family Kinases