The relative kinetics of clotting and lysis provide a biochemical rationale for the correlation between elevated fibrinogen and cardiovascular disease

Abstract

To cite this article: Kim PY, Stewart RJ, Lipson SM, Nesheim ME. The relative kinetics of clotting and lysis provide a biochemical rationale for the correlation between elevated fibrinogen and cardiovascular disease. J Thromb Haemost 2007; 5: 1250-6. Summary. Background: Elevated plasma fibrinogen is a well known risk factor for cardiovascular disease. The mechanistic rationale for this is not known. Objectives: These studies were carried out to determine the fibrinogen concentration dependencies of clotting and lysis times and thereby determine whether these times rationalize the correlation between an increased risk of cardiovascular disease and elevated plasma fibrinogen. Methods: The time courses of clot formation and lysis were measured by turbidity in systems comprising a) fibrinogen, thrombin and plasmin, or b) fibrinogen, thrombin, plasminogen and t-PA, or c) plasma, thrombin and t-PA. From the lysis times, k cat and K m values for plasmin action on fibrin were determined. Results: The time to clot increased linearly from 2.9 to 5.6 minutes as the fibrinogen concentration increased from 1 to 9 lM and did not increase further as the fibrinogen concentration was raised to 20 lM. In contrast, the clot lysis time increased linearly over the input fibrinogen concentration range of 2 to 20 lM. A similar linear trend was found in the two systems with t-PA and plasminogen. Apparent K m and k cat values for plasmin were 1.1 ± 0.6 lM and 28 ± 2 min )1 , respectively. K m values for plasmin in experiments initiated with t-PA and plasminogen were 1.6 ± 0.2 lM in the purified system and 2.1 ± 0.9 lM in plasma. Conclusion: As the concentration of fibrinogen increases, especially above physiologic level, the balance between fibrinolysis and clotting shifts toward the latter, providing a rationale for the increased risk of cardiovascular disease associated with elevated fibrinogen.

The interplay between tissue plasminogen activator domains and fibrin structures in the regulation of fibrinolysis: kinetic and microscopic studies

“…Fibrin 100 was also found to be more resistant to fibrinolysis in the "bubble release" assay format, where measurements do not depend on clot turbidity changes and tPA is incorporated throughout the clot (data not shown). In this format, there was also a small but consistent decrease in tPA potency in fibrin 100 such that tPA had 86.9% (83.1%-90.8%) potency compared with fibrin 10 .…”

“…Figure 2 shows how the potency of tPA was markedly affected by the nature of the fibrin, but the effect diminished as tPA concentration increased. In this representative example, the lowest tPA dose (0.15nM) had a more than 2-fold higher potency as plasminogen activator in fibrin 100 compared with fibrin 10 . By contrast, fibrinolysis rates in the same clots (turbidity changes in the clot, not shown) were slower in fibrin 100 such that tPA potency was calculated to be 73.8% (62.1%-87.1%) as active in fibrin 100 compared with fibrin 10 .…”

“…In this representative example, the lowest tPA dose (0.15nM) had a more than 2-fold higher potency as plasminogen activator in fibrin 100 compared with fibrin 10 . By contrast, fibrinolysis rates in the same clots (turbidity changes in the clot, not shown) were slower in fibrin 100 such that tPA potency was calculated to be 73.8% (62.1%-87.1%) as active in fibrin 100 compared with fibrin 10 . These results highlight the resistance of fine fibrin as a substrate for plasmin counter to its augmented function as a template for plasminogen activation.…”

“…7 Thrombi formed from whole blood, as opposed to purified fibrinogen and thrombin, are clearly more complex and heterogeneous environments for fibrinolysis (or thrombolysis) to occur, but the nature of the fibrin present is generally observed to resemble the coarse fiber fibrin organization seen in purified systems formed at lower thrombin concentrations. 8 Hypofibrinolysis is a risk factor for cardiovascular disease and can arise in a number of situations because of abnormal clot structure, for example, where there are high fibrinogen concentrations 9,10 or because of variants of fibrinogen that form high density fibrin clots. 11,12 However, additional constituents, such as platelets, cause local disturbances where fibrin structure becomes denser, more closely resembling the fine fibrin structures seen in clots made at high thrombin concentrations.…”

The association of plasma fibrinogen with the extent and complexity of coronary lesions in patients with acute coronary syndrome

“…In our study, we found that well known inflammatory markers that reflect vascular inflammation such as fibrinogen, hs-CRP and NLR levels were higher in patients with intermediate-high SXscore. In addition, fibrinogen contributes to blood viscosity, platelet aggregation, and fibrin formation and modulates subsequent coagulation activation [21]. Fibrinogen has been shown to promote smooth muscle cell proliferation and induce monocyte chemotaxis [22].…”