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Transforming growth factor-beta-dependent growth inhibition in primary vascular smooth muscle cells is p38-dependent

Ulrike Seay1, Daniel Sedding, Stefanie Krick

  • 1University of Giessen Lung Center, Department of Medicine I, Aulweg 123, Room 6-11, D-35392 Giessen, Germany.

The Journal of Pharmacology and Experimental Therapeutics
|August 27, 2005
PubMed

Insights

Transforming growth factor-beta (TGF-β) potently inhibits vascular smooth muscle cell (VSMC) proliferation via G0/G1 arrest, without causing apoptosis. The p38 pathway is central to this TGF-β-mediated antiproliferative effect in VSMCs.

Area of Science:

  • Vascular biology
  • Cell signaling
  • Molecular medicine

Background:

  • Vascular smooth muscle cells (VSMCs) are crucial for blood vessel structure and function.
  • VSMC proliferation contributes to vascular diseases like atherosclerosis and restenosis.
  • The role of transforming growth factor-beta (TGF-β) in regulating VSMC proliferation and apoptosis remains debated.

Purpose of the Study:

  • To investigate the precise effects of TGF-β on primary mouse VSMC proliferation and apoptosis.
  • To elucidate the specific signaling pathways involved in TGF-β-mediated regulation of VSMC growth.
  • To determine the key kinase pathways responsible for TGF-β's antiproliferative actions.

Main Methods:

  • Primary mouse VSMCs were treated with TGF-β under basal, serum-, or PDGF-BB-stimulated conditions.
  • Cell proliferation was assessed, and apoptosis was evaluated.
  • Signaling pathway activation (Smad2/3, p38, p42/44, JNK) was analyzed via phosphorylation and reporter gene assays.
  • Pharmacological inhibitors of TGF-β type I receptor (TbetaRI) kinase and specific MAP kinases were used.

Main Results:

  • TGF-β significantly inhibited VSMC proliferation without inducing apoptosis, causing cell cycle arrest at the G0/G1 phase.
  • TGF-β activated Smad2/3, p38, p42/44, and JNK signaling pathways.
  • Inhibition of TbetaRI kinase or p38 kinase attenuated TGF-β-induced growth inhibition.
  • p38 inhibition selectively blocked TGF-β's antiproliferative effect without affecting Smad signaling.

Conclusions:

  • TGF-β acts as a potent antiproliferative agent for VSMCs, irrespective of the growth stimulus, and does not induce apoptosis.
  • The antiproliferative effect is mediated by G0/G1 cell cycle arrest.
  • The p38 mitogen-activated protein kinase pathway is a critical mediator of TGF-β's growth-inhibitory function in VSMCs.

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