Specific types of activated Factor XII increase following thrombolytic therapy with tenecteplase

Bradykinin: Inflammatory Product of the Coagulation System

Episodic and recurrent local cutaneous or mucosal swelling are key features of angioedema. The vasoactive agents histamine and bradykinin are highly implicated as mediators of these swelling attacks. It is challenging to assess the contribution of bradykinin to the clinical expression of angioedema, as accurate biomarkers for the generation of this vasoactive peptide are still lacking. In this review, we will describe the mechanisms that are responsible for bradykinin production in hereditary angioedema (HAE) and the central role that the coagulation factor XII (FXII) plays in it. Evidently, several plasma parameters of coagulation change during attacks of HAE and may prove valuable biomarkers for disease activity. We propose that these changes are secondary to vascular leakage, rather than a direct consequence of FXII activation. Furthermore, biomarkers for fibrinolytic system activation (i.e. plasminogen activation) also change during attacks of HAE. These changes may reflect triggering of the bradykinin-forming mechanisms by plasmin. Finally, multiple lines of evidence suggest that neutrophil activation and mast-cell activation are functionally linked to bradykinin production. We put forward the paradigm that FXII functions as a ‘sensor molecule’ to detect conditions that require bradykinin release via crosstalk with cell-derived enzymes. Understanding the mechanisms that drive bradykinin generation may help to identify angioedema patients that have bradykinin-mediated disease and could benefit from a targeted treatment.

Role of Factor XII in hemostasis and thrombosis: clinical implications

The plasma coagulation system reacts quickly to limit blood loss from injury sites but also contributes to vascular thrombosis. In current models of hemostatic balance, normal coagulation and thrombosis represent two sides of the same coin, however, recent data from gene-deleted murine models have challenged this dogma. Deficiency of coagulation Factor XII (Hageman factor), a serine protease that initiates the intrinsic pathway of coagulation, severely impairs arterial thrombus formation but is not associated with excessive bleeding. These findings suggest that fibrin-generating mechanisms that operate during pathologic thrombus formation involve pathways distinct from those that are active during normal hemostasis. As Factor XII selectively contributes to thrombus formation in occlusive disease, but not to normal hemostasis, inhibition of this protease may offer a novel treatment strategy for prevention of arterial thrombosis with minimal or no risk of bleeding.

Activated factor XII type A predicts long-term mortality in patients admitted with chest pain

BACKGROUND

We assessed the relation between admission levels of activated factor XII type A (XIIaA), and long-term all-cause and cardiac mortality and recurrent troponin T (TnT) positive cardiovascular events in a consecutive cohort of 870 patients admitted with a clinically strongly suspected acute coronary syndrome (ACS).

METHODS AND RESULTS

After a 24-month follow-up period, 138 patients (15.8%) had died and 155 (17.8%) had suffered from a recurrent TnT positive (TnT > 0.05 ng mL(-1)) event. XIIaA levels were significantly lower in long-term survivors than in patients who died (22.9 (17.7-32.1) vs. 27.2 (20.0-39.7) pmol L(-1) [median, 25 and 75% percentiles], P < 0.001). The unadjusted hazard ratio for death within 2 years in patients with XIIaA in the highest quartile was 2.49 (95% confidence interval (CI), 1.52-4.06) as compared with patients with XIIaA in the lowest quartile. In a stepwise Cox regression model for death within 2 years, XIIaA added prognostic information for all-cause mortality (HR 2.05; 95% CI, 1.21-3.47) above and beyond age, a history of heart failure, ST-segment elevation, TnT and B-type natriuretic peptide (BNP). In the subgroup of patients with an admission TnT < or = 0.05 ng mL(-1), XIIaA provided independent prognostic information for all-cause mortality (HR 3.88; 95% CI, 1.66-9.08) and for the combined endpoint of death or recurrent TnT positive event (HR 2.46; 95% CI, 1.34-4.50).

CONCLUSION

XIIaA, a recently identified in vivo form of activated factor XII is an independent indicator of long-term all-cause mortality in patients admitted with chest pain, providing prognostic information above and beyond conventional risk factors.

Changes of plasma activated Factor XII type A (XIIaA) concentrations following percutaneous coronary intervention (PCI)

BACKGROUND

Recent research has demonstrated that in-vivo XIIa exists in a number of different types and that treatment with tenecteplase increases the plasma concentration of XIIaA. Only limited data exist on changes in activated Factor XII (XIIa) levels following mechanical revascularisation, such as percutaneous coronary intervention (PCI).

METHODS

Citrated blood samples were obtained from 31 PCI-treated patients admitted with ST-elevation myocardial infarction (STEMI) and 20 patients undergoing elective PCI. Samples were taken immediately before the invasive procedure, 30-90 min after PCI and (in patients undergoing primary PCI) 4-6 days following intervention. Additional samples were taken after angiography, just prior to the follow-on PCI procedure, in 16 of the patients undergoing elective PCI, to investigate possible effects of contrast fluid and heparin. XIIa measurements were performed using 2 ELISA assays designed to preferentially measure different types of XIIa; XIIaA and XIIaR.

RESULTS

In the group undergoing primary PCI, XIIaA showed a significant increase from 68 (48-93) pM in the pre-treatment sample to 100 (75-123) pM [median and 25- and 75% percentiles] in the 30-90-min post-treatment sample (p < 0.001), returning to pre-intervention levels by day 4-6. A similar increase in XIIaA was obtained in patients undergoing elective PCI. In contrast, no significant changes in XIIaR concentration were observed. Whilst XIIaA concentrations remained unchanged in 6 non-heparinised patients undergoing elective coronary angiography, XIIaA levels rose significantly from 56 (51-75) pM to 98 (71-125) pM [median and 25- and 75% percentiles], (p < 0.01) in 10 patients after the addition of heparin.

CONCLUSION

A significant short-lasting increase in specific types of XIIa (namely XIIaA) was observed following PCI. These increases are most likely induced by the concomitant treatment with heparin.

Specific types of activated Factor XII increase following thrombolytic therapy with tenecteplase

BACKGROUND

Activated Factor XII (XIIa) is believed to participate in a number of pathophysiological processes including inflammation, thrombosis and fibrinolysis. Increasing XIIa levels following thrombolytic therapy have previously been reported. In contrast to other thrombolytics, tenecteplase (TNK-tpa) does not show paradoxical thrombin activation, indicating a lower procoagulant effect of this fibrin-selective thrombolytic agent. Recent research has demonstrated that in-vivo XIIa exists in a number of different types, and the aim of this study was to investigate plasma variations of different types of XIIa following thrombolytic treatment with TNK-tpa.

METHODS

Citrated blood samples were obtained from 34 patients admitted with acute ST-elevation myocardial infarction (STEMI) treated with TNK-tpa. Samples were taken immediately prior to treatment, 30-90 min after and 4 days post-treatment. XIIa measurements were performed using 2 ELISA assays designed to preferentially measure different types of XIIa; XIIaA and XIIaR. Both assays utilised a monoclonal antibody 2/215, which is highly specific for XIIa, as the solid phase capture antibody. The assay for XIIaA used a conjugate based on a polyclonal antibody against the entire XIIa molecule, whilst the assay for XIIaR incorporated a reagent to release otherwise unavailable XIIa and used a conjugate based on a monoclonal antibody against beta-XIIa.

RESULTS

Changes in plasma XIIaA concentration as a result of therapy were more evident than changes in XIIaR concentration. XIIaA showed a significant increase from 67.1 (49.0-84.4) pM to 97.8 (75.5-133.1) pM [median and 25 and 75% percentiles] in the 30-90 min sample (P < 0.001), returning to pre-intervention levels 61.5 (47.5-81.0) pM by day 4. In contrast, no significant change in XIIaR concentration was observed following thrombolytic therapy with TNK-tpa.

CONCLUSION

In patients admitted with STEMI, thrombolytic therapy with TNK-tpa resulted in a significant short-lasting increase in specific types of XIIa (namely XIIaA), whereas other types of XIIa (XIIaR) were largely unaffected by this intervention.