Spearman correlation of angiopoietin-1 and VEGF with other parameters.

†<p>p<0.05.</p>‡<p><0.01.</p

Characteristics of malaria patients and controls.

<p>Shown are medians with interquartile range unless otherwise specified.</p><p>ns, not significant (P>0.05); NA, not applicable.</p

Platelet number and plasma levels of angiogenic and platelet activation markers.

<p>Levels of angiopoietin-2, angiopoietin-1, vascular endothelial growth factor (VEGF), soluble P-selectin and CXCL7 were determined in CTAD plasma in 27 patients with febrile <i>P. falciparum</i> malaria at the start of malaria treatment (day 0), day 2 and day 5 and in 25 healthy controls. Data are presented in a scatter dot plot with median and interquartile range. Differences between malaria patients in time were assessed by the Friedman’s test; differences with controls with the Mann-Whitney test. **denotes p<0.01 and *p<0.05.</p

Platelet Activation Determines Angiopoietin-1 and VEGF Levels in Malaria:Implications for Their Use as Biomarkers

<p>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.</p><p>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.</p><p>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.</p><p>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.</p>