Involvement of placental growth factor upregulated via TGF-β1-ALK1-Smad1/5 signaling in prohaptoglobin-induced angiogenesis

PLoS One. 2019 Apr 29;14(4):e0216289. doi: 10.1371/journal.pone.0216289. eCollection 2019.

Abstract

A potential role of haptoglobin in arterial restructuring has been suggested, and our previous study demonstrated that prohaptoglobin, the precursor of haptoglobin, stimulates endothelial angiogenesis. However, the mechanisms underlying the angiogenic effects of prohaptoglobin are still unclear. Here, we investigated angiogenic signaling induced by prohaptoglobin using human umbilical vein endothelial cells. Prohaptoglobin upregulated the expression of placental growth factor (PlGF), vascular endothelial growth factor (VEGF)-A, and VEGF receptor 1 and 2, and also induced cell migration and tube network formation. PlGF knockdown attenuated these angiogenic effects of prohaptoglobin. Furthermore, a transcription factor profiling assay indicated that Smad is involved in PlGF expression in response to prohaptoglobin. Transforming growth factor-β1 (TGF-β1) expression and Smad1/5 phosphorylation were also induced by prohaptoglobin treatment. Blockade of TGF-β1 signaling using the TGF-β receptor kinase inhibitor LY2109761 or Smad1/5 siRNA reduced the prohaptoglobin-induced PlGF expression and in vitro tube formation. Knockdown of the TGF-β receptor ALK1, but not ALK5, with a specific siRNA blocked the Smad1/5 phosphorylation and PlGF expression induced by prohaptoglobin. These findings suggest that the angiogenic effects of prohaptoglobin are dependent on PlGF and mediated via a TGF-β1-ALK1-Smad1/5-PlGF/VEGFR1-VEGF-A/VEGFR2 signaling pathway.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Activin Receptors, Type II / metabolism*
  • Animals
  • COS Cells
  • Chlorocebus aethiops
  • Haptoglobins / metabolism*
  • Human Umbilical Vein Endothelial Cells / metabolism
  • Humans
  • Models, Biological
  • Neovascularization, Physiologic*
  • Placenta Growth Factor / metabolism*
  • Protein Precursors / metabolism*
  • Signal Transduction
  • Smad Proteins / metabolism*
  • Transforming Growth Factor beta1 / metabolism*
  • Up-Regulation*
  • Vascular Endothelial Growth Factor A / metabolism
  • Vascular Endothelial Growth Factor Receptor-2 / metabolism

Substances

  • Haptoglobins
  • PGF protein, human
  • Protein Precursors
  • Smad Proteins
  • Transforming Growth Factor beta1
  • Vascular Endothelial Growth Factor A
  • prohaptoglobin
  • Placenta Growth Factor
  • Vascular Endothelial Growth Factor Receptor-2
  • ACVRL1 protein, human
  • Activin Receptors, Type II

Grants and funding

This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT).(2016R1A2B1009425; Recipient:ISK). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.