Characterisation and the effects of bilirubin binding to human fibrinogen

Abstract

Fibrinogen, a protein involved in blood coagulation, is very susceptible to oxidation. Oxidation alters its function and usually makes it more thrombogenic. Bilirubin, an end-product of the haem degradation in vertebrates, is known for its antioxidant properties. The present paper describes interaction between fibrinogen and bilirubin, and the influence of bilirubin on the formation of fibrin and protection against oxidation. The binding constant of 4.5 x 10 4 M-1 was determined for the fibrinogen/bilirubin complex at 37 °C. There is no change in secondary and tertiary structure of fibrinogen or its thermal stability upon bilirubin binding. The binding site of fibrinogen is not stereospecific for bilirubin and is able to accommodate both bilirubin conformers. A change in absorption maximum of bilirubin occurs upon its interaction with fibrinogen, suggesting an alteration in the conformation of bilirubin to the more cyclic one. Bilirubin exerts antioxidant effect on fibrinogen, preventing its carbonylation and aggregation. The presence of bilirubin induces the formation of fibrin with thicker fibres, as assessed by the coagulation assay. Fibrinogen and bilirubin interact at physiological concentrations, bilirubin may act as an antioxidant for fibrinogen and may modulate an important event in haemostasis, which altogether suggests possible physiological relevance of this interaction.

Fibrinogen Increases Resveratrol Solubility and Prevents it from Oxidation

“…It seems that the amount of α-helixes, the most dominant secondary structure of fibrinogen, remains the same during resveratrol binding. Similar results were obtained when human fibrinogen was incubated with bilirubin [12]. However, the interaction of resveratrol with bovine…”

“…It seems that the amount of α-helixes, the most dominant secondary structure of fibrinogen, remains the same during resveratrol binding. Similar results were obtained when human fibrinogen was incubated with bilirubin [12]. However, the interaction of resveratrol with bovine Similar melting temperatures were obtained for fibrinogen alone or in the presence of resveratrol ( Figure 3A,B), suggesting that resveratrol does not significantly (p > 0.05) affect fibrinogen folding and stability.…”

“…It seems that the amount of α-helixes, the most dominant secondary structure of fibrinogen, remains the same during resveratrol binding. Similar results were obtained when human fibrinogen was incubated with bilirubin [12]. However, the interaction of resveratrol with bovine fibrinogen decreases the α-helical content in the protein [20], suggesting that a different interaction mechanism occurs compared to human fibrinogen.…”

“…During secondary hemostasis, fibrinogen is converted to fibrin by thrombin, which removes fibrinopeptides A and B, forming fibrin monomers that associate with one another, creating a fibrin network that serves to mechanically reinforce the blood clot [7]. Many factors influence fibrin formation and, consequently, its degradation, including the types of fibrinogen chain [10], the glycosylation of fibrin [11], and the interactions with other proteins [7] and small molecules [12].…”

Thromboinflammatory mechanisms in sickle cell disease - challenging the hemostatic balance

“…With regards to final clot formation, hemolysis has been suggested to exacerbate hyperfibrinolysis and facilitate uncontrolled bleeding, with red cell lysate accentuating tissue plasminogen activator-mediated fibrinolysis 86 In contrast, hematin and the products of heme degradation, iron, bilirubin and carbon monoxide, are known to interact with fibrinogen, and induce fibrin formation or decrease fibrinolysis, possibly accelerating the formation of resistant clots. 83 , 87 , 88 As such, heme has a clear role in triggering the initiation of coagulation, although its effects on the propagation of this system are not as well understood. 69 …”