Characterization and effects of metal-chelate-heparin complexes with relevance to vascular restenosis.

摘要

The interaction between metal chelate compounds and heparin was investigated using spectroscopic and chemical techniques, and the effect of metal chelate binding on ex vivo and in vivo effects of heparin determined in a rat model of restenosis. It was found that iron (III) acetylacetone interacts preferentially with heparin in a 1:1 mole ratio of iron chelate/hexosamine residue. Binding was the result of a combination of electrostatic and non-electrostatic forces. The association of iron acetylacetone and heparin was confirmed by light scattering showing the formation of a complex of high molecular weight.; Ex vivo studies indicated no difference in activity against thrombin and factor Xa between the complex and heparin alone; however, a protective role of complexed heparin against the effect of metal ions on LDL oxidation was observed.; In vivo studies revealed that the formation of the iron acetylacetone-heparin complex changed the kinetics of disposition of heparin after intravenous administration to rats apparently{09}as a result of increased binding to endothelium. In addition, the antiproliferative effects of the complex were assessed in a rat carotid artery model of restenosis induced by air. Histological analysis of carotid artery segments showed that air effectively damaged the endothelial lining and the rate of endothelial regeneration was faster in drug treated groups compared to control. Finally, the rate of smooth muscle cell proliferation, measured by the extent of arterial wall thickening, was evaluated by monitoring a marker of thrombosis (Tissue Factor Pathway inhibitor, TFPI) and a marker of vascular damage (fibronectin, FN). Metal-chelate heparin complex produced a sustained depletion of plasma TFPI activity compared to heparin alone in a seven-day experimental period. This result was explained as heparin changes in its kinetics of disposition. A correlation between the extent of vascular proliferation and FN levels was evidenced in no drug treated group indicating that FN may have the potential of a circulating marker of restenosis progression. Results from heparin treated and complex treated groups showed no significant differences and steady levels of FN. These results were corroborated by histological cross section analysis of treated segments.