Blood, 15 March 2002, Vol. 99, No. 6, pp. 2221-2227
PHAGOCYTES
High-affinity binding sites for heparin generated on leukocytes
during apoptosis arise from nuclear structures segregated during cell
death
Milena A. Gebska,
Ian Titley,
Hugh F. Paterson,
Ricardo M. Morilla,
Derek C. Davies,
Alicja M. Gruszka-Westwood,
Vijay V. Kakkar,
Suzanne Eccles, and
Michael F. Scully
From the Coagulation and Fibrinolysis Laboratory,
Thrombosis Research Institute, Emmanuel Kaye Building, London; Leukemia
Research Fund Centre, Institute of Cancer Research, London; Cell Centre
for Cell and Molecular Biology, Institute of Cancer Research, London;
Academic Department of Haematology and Cytogenetics, The Royal Marsden
Hospital, London; FACS Laboratory, Imperial Cancer Research Fund,
London; and Tumour Biology and Metastases Section of Cancer
Therapeutics, Institute of Cancer Research, Sutton, United Kingdom.
During cell death of human cultured leukocytes (Jurkat, HL-60,
THP-1, U937) and freshly prepared leukocytes, we observed a greater
than 100-fold increase in the affinity of apoptotic and necrotic cells
for fluorescein isothiocyanate (FITC)-heparin in comparison with live
cells. Binding of FITC-heparin was reversed in the presence of high
ionic strength, unlabeled heparan sulfate, and heparin and pentosan
polysulfate, but not in the presence of chondroitin and dermatan
sulfates. During the course of cell death, the increase in the
percentage of cells positive for annexin V binding correlated with the
increase in the population positive for binding FITC-heparin. Confocal
microscopy demonstrated that heparin binding to dead cells was
restricted to 1 or 2 small domains on the surfaces of apoptotic cells
and to larger, but still discrete, areas that did not localize with
chromatin on ruptured necrotic cells. The heparin-binding domains
originated from the nucleus and may correspond to the
ribonucleoprotein-containing structures that have recently been shown
to segregate within the nucleus of cells and to move onto the cell
membrane. We observed that phagocytosis of dead Jurkat cells by
monocyte-derived macrophages was blocked when the heparin-binding
capacity of the dead cells was saturated by the addition of pentosan
polysulfate. From this we concluded that the ability of dead cells to
bind to heparan sulfate proteoglycans on the surfaces of macrophages
may assist in phagocytic clearance.
