Platelet activation determines angiopoietin-1 and VEGF levels in malaria: implications for their use as biomarkers

PLoS One. 2013 Jun 3;8(6):e64850. doi: 10.1371/journal.pone.0064850. Print 2014.

Abstract

Introduction: The angiogenic proteins angiopoietin (Ang)-1, Ang-2 and vascular endothelial growth factor (VEGF) are regulators of endothelial inflammation and integrity. Since platelets store large amounts of Ang-1 and VEGF, measurement of circulation levels of these proteins is sensitive to platelet number, in vivo platelet activation and inadvertent platelet activation during blood processing. We studied plasma Ang-1, Ang-2 and VEGF levels in malaria patients, taking the necessary precautions to avoid ex vivo platelet activation, and related plasma levels to platelet count and the soluble platelet activation markers P-selectin and CXCL7.

Methods: Plasma levels of Ang-1, Ang-2, VEGF, P-selectin and CXCL7 were measured in CTAD plasma, minimizing ex vivo platelet activation, in 27 patients with febrile Plasmodium falciparum malaria at presentation and day 2 and 5 of treatment and in 25 healthy controls.

Results: Levels of Ang-1, Ang-2 and VEGF were higher at day 0 in malaria patients compared to healthy controls. Ang-2 levels, which is a marker of endothelial activation, decreased after start of antimalarial treatment. In contrast, Ang-1 and VEGF plasma levels increased and this corresponded with the increase in platelet number. Soluble P-selectin and CXCL7 levels followed the same trend as Ang-1 and VEGF levels. Plasma levels of these four proteins correlated strongly in malaria patients, but only moderately in controls.

Conclusion: In contrast to previous studies, we found elevated plasma levels of Ang-1 and VEGF in patients with malaria resulting from in vivo platelet activation. Ang-1 release from platelets may be important to dampen the disturbing effects of Ang-2 on the endothelium. Evaluation of plasma levels of these angiogenic proteins requires close adherence to a stringent protocol to minimize ex vivo platelet activation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Angiopoietin-1 / blood*
  • Biomarkers / blood
  • Case-Control Studies
  • Child
  • Female
  • Humans
  • Malaria / blood*
  • Male
  • Platelet Activation*
  • Platelet Count
  • Statistics, Nonparametric
  • Vascular Endothelial Growth Factor A / blood*
  • Young Adult

Substances

  • ANGPT1 protein, human
  • Angiopoietin-1
  • Biomarkers
  • VEGFA protein, human
  • Vascular Endothelial Growth Factor A

Grant support

Research support from the KNAW (Royal Academy of Sciences) through the SPIN Postdoc Research Programme (RN) and the Noaber foundation and Augeo foundation (JB, QM). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.