CXCL4L1 inhibits angiogenesis and induces undirected endothelial cell migration without affecting endothelial cell proliferation and monocyte recruitment.
OBJECTIVE
The non-allelic variant of CXCL4/PF4, CXCL4L1/PF4alt, differs from CXCL4 in three amino acids of the C-terminal α-helix and has been characterized as a potent anti-angiogenic regulator. Although CXCL4 structurally belongs to the chemokine family, it does not behave like a 'classical' chemokine, lacking significant chemotactic properties. Specific hallmarks are its angiostatic, anti-proliferative activities, and proinflammatory functions, which can be conferred by heteromer-formation with CCL5/RANTES enhancing monocyte recruitment.


RESULTS
Here we show that tube formation of endothelial cells was inhibited by CXCL4L1 and CXCL4, while only CXCL4L1 triggered chemokinesis of endothelial cells. The chemotactic response towards VEGF and bFGF was attenuated by both variants and CXCL4L1-induced chemokinesis was blocked by bFGF or VEGF. Endothelial cell proliferation was inhibited by CXCL4 (IC(50) 6.9 μg mL(-1)) but not by CXCL4L1, while both chemokines bound directly to VEGF and bFGF. Moreover, CXCL4 enhanced CCL5-induced monocyte arrest in flow adhesion experiments and monocyte recruitment into the mouse peritoneal cavity in vivo, whereas CXCL4L1 had no effect. CXCL4L1 revealed lower affinity to CCL5 than CXCL4, as quantified by isothermal fluorescence titration. As evidenced by the reduction of the activated partial thromboplastin time, CXCL4L1 showed a tendency towards less heparin-neutralizing activity than CXCL4 (IC(50) 2.45 vs 0.98 μg mL(-1)).


CONCLUSIONS
CXCL4L1 may act angiostatically by causing random endothelial cell locomotion, disturbing directed migration towards angiogenic chemokines, serving as a homeostatic chemokine with a moderate structural distinction yet different functional profile from CXCL4.
Sarabi
A
A
Institute for Cardiovascular Molecular Research, University Hospital Aachen, RWTH Aachen University, Aachen, Germany.
Kramp
B K
BK
Drechsler
M
M
Hackeng
T M
TM
Soehnlein
O
O
Weber
C
C
Koenen
R R
RR
Von Hundelshausen
P
P
D043165:Angiostatic Proteins / Q000138:chemical synthesis / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001777:Blood Coagulation; D002465:Cell Movement; D049109:Cell Proliferation; D002478:Cells, Cultured; D018946:Chemokine CCL5 / Q000378:metabolism; D002634:Chemotaxis, Leukocyte; D042783:Endothelial Cells / Q000276:immunology*; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism; D006801:Humans; D018836:Inflammation Mediators / Q000138:chemical synthesis / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D009000:Monocytes / Q000276:immunology*; D018919:Neovascularization, Physiologic; D010314:Partial Thromboplastin Time; D010978:Platelet Factor 4 / Q000138:chemical synthesis / Q000235:genetics / Q000378:metabolism*; D055503:Protein Multimerization; D011994:Recombinant Proteins / Q000378:metabolism; D013997:Time Factors; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
D043165:Angiostatic Proteins; D018946:Chemokine CCL5; D018836:Inflammation Mediators; C064936:PF4V1 protein, human; D011994:Recombinant Proteins; D042461:Vascular Endothelial Growth Factor A; D016222:Fibroblast Growth Factor 2; D010978:Platelet Factor 4