Importance of size and sulfation of heparin in release of basic fibroblast growth factor from the vascular endothelium and extracellular matrix

Abstract

We have characterized the importance of size, sulfation, and anticoagulant activity of heparin in release of basic fibroblast growth factor (bFGF) from the subendothelial extracellular matrix (ECM) and the luminal surface of the vascular endothelium. For this purpose, 125I-bFGF was first incubated with ECM and confluent endothelial cell cultures, or administered as a bolus into the blood of rats, the immobilized 125I-bFGF was then subjected to release by various chemically modified species of heparin and size-homogeneous oligosaccharides derived from depolymerized heparin. Both totally desulfated and N-desulfated heparin failed to release the ECM-bound bFGF. Likewise, substitution of N-sulfate groups of heparin and low molecular weight heparin (fragmin) by acetyl or hexanoyl residues resulted in an almost complete inhibition of bFGF release by these polysaccharides. The presence of O-sulfate groups in heparin increased but was not critical for release of ECM-bound bFGF. Similar structural requirements were identified for release of 125I-bFGF bound to low-affinity sites on the surface of vascular endothelial cells. Oligosaccharides derived from depolymerized heparin and containing as little as 8-10 sugar units were, on a weight basis, equivalent to whole heparin in their ability to release bFGF from ECM. Low-sulfate oligosaccharides were less effective releasers of bFGF as compared to medium- and high-sulfate fractions of the same size oligosaccharides. Heparin fractions with high and low affinity to antithrombin III exhibited a similar high bFGF-releasing activity despite a 200-fold difference in their anticoagulant activities.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative Study In Vivo and In Vitro of Uniformly 14C‐Labelled and 125I‐Labelled Recombinant Fibroblast Growth Factor 2

“…This accumulation of radiolabelling was probably not due to a redistribution of FGF2. Blood halflife of FGF2 is lower than 5 min (Hondermarck et al, 1990;Whalen eta]., 1989;Ishai-Michaeli et al, 1992;Edelman et al, 1993). Therefore, the increased "'I-FGF2 labelling of thyroid with time is very likely due to a displacement of the radioactive element (i.e.…”

“…The pharmacokinetic profile of a given growth factor can be indirectly measured by counting the organ-bound radioactivity after injection of iodinated tracer (Klapproth et al, 1989;Beutler et al, 1985;Zioncheck et al, 1994;Hondermarck et al, 1990;Edelman et al, 1993;Newton et al, 1988). However, this measurement does not give a real indication of the tissue distribution of the given growth factor.…”

Vascular growth factor binding kinetics to the endothelial cell basement membrane, with a kinetics-based correction for substrate binding

“…Vascular endothelial growth factor (VEGF) and fibroblast growth factor-2 (FGF-2) bind to heparan sulfate proteoglycans in the basement membrane, where they are protected from degradation and non-enzymatic glycosylation (Vlodavsky et al 1987;Folkman et al 1988;Houck et al 1992;Murdoch et al 1992;Park et al 1993;Poltorak et al 1997;Nissen et al 1999). When growth factors are later released by heparatinase, heparin-like molecules, thrombin, or other proteases, they stimulate proliferation, migration or survival in neighboring cells (Bashkin et al 1989;Ishai-Michaeli et al 1992;Benezra et al 1993;Whitelock et al 1996).…”

Modulation of the Heparanase-inhibiting Activity of Heparin through Selective Desulfation, Graded N-Acetylation, and Glycol Splitting

“…As a general trend, the heparanase-inhibiting activity increases with increasing degrees of O-sulfation. However, N-sulfates seems to exert little effect since they can be replaced by N-acyl (N-acetyl, N-succinyl, or N-hexanoyl) groups without substantial loss of inhibitory activity (20,34). No significant differences were found between the currently used unfractionated heparins and low molecular weight heparins and a tetradecasaccharidic fragment (34).…”

“…However, N-sulfates seems to exert little effect since they can be replaced by N-acyl (N-acetyl, N-succinyl, or N-hexanoyl) groups without substantial loss of inhibitory activity (20,34). No significant differences were found between the currently used unfractionated heparins and low molecular weight heparins and a tetradecasaccharidic fragment (34). 2-ODesulfated derivatives were shown to retain the inhibitory activity, whereas N-desulfated, N-acetylated derivatives displayed a reduced activity (35).…”