Incorporation of α2-Plasmin Inhibitor into Fibrin Clots and Its Association with the Clinical Outcome of Acute Ischemic Stroke Patients

Abstract

Cross-linking of α2-plasmin inhibitor (α2-PI) to fibrin by activated factor XIII (FXIIIa) is essential for the inhibition of fibrinolysis. Little is known about the factors modifying α2-PI incorporation into the fibrin clot and whether the extent of incorporation has clinical consequences. Herein we calculated the extent of α2-PI incorporation by measuring α2-PI antigen levels from plasma and serum obtained after clotting the plasma by thrombin and Ca2+. The modifying effect of FXIII was studied by spiking of FXIII-A-deficient plasma with purified plasma FXIII. Fibrinogen, FXIII, α2-PI incorporation, in vitro clot-lysis, soluble fibroblast activation protein and α2-PI p.Arg6Trp polymorphism were measured from samples of 57 acute ischemic stroke patients obtained before thrombolysis and of 26 healthy controls. Increasing FXIII levels even at levels above the upper limit of normal increased α2-PI incorporation into the fibrin clot. α2-PI incorporation of controls and patients with good outcomes did not differ significantly (49.4 ± 4.6% vs. 47.4 ± 6.7%, p = 1.000), however it was significantly lower in patients suffering post-lysis intracranial hemorrhage (37.3 ± 14.0%, p = 0.004). In conclusion, increased FXIII levels resulted in elevated incorporation of α2-PI into fibrin clots. In stroke patients undergoing intravenous thrombolysis treatment, α2-PI incorporation shows an association with the outcome of therapy, particularly with thrombolysis-associated intracranial hemorrhage.

Low α2-Plasmin Inhibitor Antigen Levels on Admission Are Associated With More Severe Stroke and Unfavorable Outcomes in Acute Ischemic Stroke Patients Treated With Intravenous Thrombolysis

“…Nevertheless, these results suggest that α2-PI could play a role in the pathophysiology of thrombolysis failure and may be an important factor contributing to the inefficacy of therapy in case of severe strokes. Consistent with this finding, we have shown in previous work that the extent of α2-PI incorporation into fibrin clots was the lowest in AIS patients with favorable outcomes after thrombolysis (10). These results are in line with another recent work from our group where we showed that together with age and NIHSS, thrombus burden is the most important indicator of thrombolysis outcome, and the levels of a number of key hemostasis parameters measured on admission or 24 h later showed no association with treatment outcomes in a multivariate model (46).…”

“…Interestingly, on admission, only moderately strong correlation was found between the activity and antigen assay results, which then improved post-lysis. This might arise from the fact that the incorporation of α2-PI into the thrombus by FXIIIa primarily involves PB-α2-PI (10,43). It has been suggested by previous reports that the commercially available chromogenic α2-PI activity assay used in this study is mainly sensitive to the levels of PB-α2-PI, the more active and kinetically faster plasmin inhibitor (44,45).…”

“…The buffy coat of blood samples was used to extract genomic DNA based on standard protocols (QIAamp DNA Blood Mini Kit, Qiagen, Hilden, Germany). The α2-PI Arg6Trp (rs2070863) polymorphism was identified by real-time PCR using fluorescence resonance energy transfer detection and melting curve analysis on a LightCycler R 480 instrument as described previously (Roche Diagnostics GmbH, Mannheim, Germany; primers are available from the authors upon request) (10). α2-PI activity and antigen level assays as well as the determination of α2-PI Arg6Trp genotype were carried out by investigators blinded to patient identification and clinical data.…”

“…As the fibrinolytic system provides the very basis of the mechanism of thrombolysis, it can be surmised that individual factors altering lysis susceptibility are likely to be key contributors to recanalization failure and bleeding complications. Surprisingly, our knowledge to date regarding this aspect is limited to a few reports (10)(11)(12)(13)(14)(15).…”

Predictive value of coagulation factor XIII on bleeding risk in ischemic stroke patients treated with intravenous thrombolysis

“…Two recent studies have shown a survival increase for FXIII substitution in trauma patients, suggesting the potential effectiveness of FXIII for the treatment of hemorrhage (37,38). Moreover, increased FXIII levels may result in elevated incorporation of α2plasmin inhibitor (α2-PI), showing an association with the outcome of IVT therapy (39). Therapeutic plasma exchange or albumin solutions enriched FXIII, and purified plasma-derived FXIII may restore coagulation potential, which may be a promising treatment strategy and merits further verification (40,41,42).…”