Relationship Between The Structure And Anti-Thrombotic Mechanism Of Heparin-Derived Oligosaccharides

Heparin belongs to glycosaminoglycan (GAGs), which is comprised of alternating 1→4 lined uronic acid and glucosamine residue. Its major repeating disaccharide unit is -[-α-L-IdoA-2-SO₄-(1→4)-αD-G1cNSO₃-6-SO₄-]-, and its relative molecular weights can range from 3 kD to 30 kD. Heparin oligosaccharides are the products produced by degradation of heparin and their average relative molecular weights between 1 kD to 4 kD.Thrombosis diseases are one kind of syndrome which is induced by blood coagulation in vascular or heart tissues that damaged the blood-flowing to some extent. Heparin has been used mainly for the prophylaxis and treatment of thrombosis diseases clinically for 70 years, while unfractionated heparin has side effects such as hemorrhage and thrombopenia. Preparations of LMW-heparin have been shown to have several advantages over unfractionated heparin. One of the most advantages of LMW-heparin is the fact that these preparations seem to cause less bleeding.In order to study the relationship between the structure of heparin oligosaccharides and their anti-thrombosis effects, heparin oligosaccharides with different molecular weights and structures are prepared byβ-elimination degradated heparin and then separated and purified by Bio-gel P6 size exclusive chromatography method. Determine the structure of oligosaccharides and study their influences on platelets, P-selectins and von willebrand factors, investigating the mechanism of heparin oligosaccharides' anti-thrombosis effects.The results and conclusions of this study:1. The heparin oligosaccharides are prepared byβ-elimination degradation. The four relatively pure heparin oligosaccharides HO-1, HO-2, HO-3 and HO-4 were purified with Bio-gel P6 gel chromatography.2. The major structures of HO-1, HO-2, HO-3 and HO-4 were determined by UV, infrared spectra (IR), NMR spectra (¹³C-NMR and ¹H-NMR) and disaccharide analysis.3. Determine the physical and chemical properties of the four heparin oligosaccharides HO-1, HO-2, HO-3 and HO-4 partly. Their relative average molecular weight are 3356, 2061, 1614 and 1297 respectively; the ratio ofSO ₄^2- /COO- are 2.42, 2.0, 1.67 and 2.51 respectively; the content of glycuronic acidare 36.52%, 33.9%, 43.75%and 38.5% respectively; the anti-coagulation potency is 33 USPU/mg, 9 USPU/mg, 5 USPU/mg and 4 USPU/mg respectively; the anti-FXa activity is 62 IU/mg, 40 IU/mg, 25 IU/mg and 15 IU/mg, the specific optical rotations are 43.08, 33.27, 26.17 and 12.83 respectively.4. The anti-thrombosis study shows that:â‘ HO-1, HO-2, HO-3 and HO-4 can inhibit the assembling of platelets at the dose of 81.4 mg/ml.â‘¡HO-1, HO-2, HO-3 and HO-4 can inhibit the release of P-selectin and von willebrand factor.â‘¢The effects of heparin oligosaccharides on protein C activity in plasma showed that HO-1, HO-2, HO-3 and HO-4 can enhance the activity of protein C, HO-1 posses the strongest effects.