Macrophages contribute to the cellular uptake of von Willebrand factor and factor VIII in vivo.
Von Willebrand factor (VWF) and factor VIII (FVIII) circulate in a tight noncovalent complex. At present, the cells that contribute to the removal of FVIII and VWF are of unknown identity. Here, we analyzed spleen and liver tissue sections of VWF-deficient mice infused with recombinant VWF or recombinant FVIII. This analysis revealed that both proteins were targeted to cells of macrophage origin. When applied as a complex, both proteins were codirected to the same macrophages. Chemical inactivation of macrophages using gadolinium chloride resulted in doubling of endogenous FVIII levels in VWF-null mice, and of VWF levels in wild-type mice. Moreover, the survival of infused VWF was prolonged almost 2-fold in VWF-deficient mice after gadolinium chloride treatment. VWF and FVIII also bound to primary human macrophages in in vitro tests. In addition, radiolabeled VWF bound to human THP1 macrophages in a dose-dependent, specific, and saturable manner (half-maximal binding at 0.014 mg/mL). Binding to macrophages was followed by a rapid uptake and subsequent degradation of the internalized protein. This process was also visualized using a VWF-green fluorescent protein fusion protein. In conclusion, our data strongly indicate that macrophages play a prominent role in the clearance of the VWF/FVIII complex.
van Schooten
Carina J
CJ
Department of Clinical Chemistry and Haematology, University Medical Center Utrecht, Utrecht, The Netherlands.
Shahbazi
Shirin
S
Groot
Evelyn
E
Oortwijn
Beatrijs D
BD
van den Berg
H Marijke
HM
Denis
Cécile V
CV
Lenting
Peter J
PJ
D000818:Animals; D001693:Biological Transport, Active; D005169:Factor VIII / Q000235:genetics / Q000378:metabolism*; D005682:Gadolinium / Q000494:pharmacology; D006801:Humans; D008099:Liver / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013154:Spleen / Q000378:metabolism; D014841:von Willebrand Factor / Q000235:genetics / Q000378:metabolism*
D011994:Recombinant Proteins; D014841:von Willebrand Factor; D005169:Factor VIII; D005682:Gadolinium; C038958:gadolinium chloride