Lecanemab blocks the effects of the Aβ/fibrinogen complex on blood clots and synapse toxicity in organotypic culture

Abstract

Proteinaceous brain inclusions, neuroinflammation, and vascular dysfunction are common pathologies in Alzheimer's disease (AD). Vascular deficits include a compromised blood-brain barrier, which can lead to extravasation of blood proteins like fibrinogen into the brain. Fibrinogen's interaction with the amyloid-beta (Aβ) peptide is known to worsen thrombotic and cerebrovascular pathways in AD. Lecanemab, an FDA-approved antibody therapy for AD, clears Aβ plaque from the brain and slows cognitive decline. Here, we show that lecanemab blocks fibrinogen's binding to Aβ protofibrils, preventing Aβ/fibrinogen-mediated delayed fibrinolysis and clot abnormalities in vitro and in human plasma. Additionally, we show that lecanemab dissociates the Aβ/fibrinogen complex and prevents fibrinogen from exacerbating Aβ-induced synaptotoxicity in mouse organotypic hippocampal cultures. These findings reveal a possible protective mechanism by which lecanemab may slow disease progression in AD.

Keywords: Alzheimer’s disease; amyloid-beta; fibrinogen; fibrinolysis; lecanemab.

Fig. 1.

Lecanemab restores Aβ42-induced delayed fibrinolysis and clot abnormalities by inhibiting the Aβ42/fibrinogen interaction in vitro. (A) Biotinylated Aβ42 protofibrils (B-Aβ42) bind to fibrinogen-coated wells. (B) Lecanemab dose-dependently blocked the binding of B-Aβ42 to fibrinogen, while human IgG had no effect. (C) Quantification of B (at equimolar ratio). (A–C) Data from three independent experiments, n = 8 to 16/group. (D) Transmission EM of Aβ42 protofibrils. (Scale bar, 200 nm.) (E) Turbidity assay shows clotting and clot lysis phases. Lecanemab, but not control IgG, corrected the Aβ42-induced delayed fibrinolysis. (F) Quantification of clot lysis rate in E (slope between vertical dotted lines). (G) Quantification of maximum clot turbidity in E. (E–G) Data from six independent experiments, n = 6/group. (H) Representative scanning EM of fibrin clots from purified fibrinogen with different treatments. (Scale bar, 10 µm.) (I and J) Quantification of fibrin diameter and total area of abnormal fibrin clumps in clot images. Data from three independent experiments. Vehicle constitutes PBS+DMSO. Comparisons among multiple groups were performed using one-way ANOVA followed by Newman–Keuls multiple comparison test. Data are presented as mean ± SEM. ****P < 0.0001, ***P < 0.001; ns, not significant.

Fig. 2.

Lecanemab blocks Aβ42-induced clot abnormalities and delays fibrinolysis in NHP and Aβ42/fibrinogen-mediated synaptotoxicity in mouse OHC. (A) Biotinylated Aβ protofibrils (B-Aβ42) immunoprecipitated fibrinogen from NHP but did not in the presence of lecanemab. (B) Quantification of A. Data from three independent experiments; n = 8/group. (C) Clotting and fibrinolysis in NHP using turbidity assay. Lecanemab restored Aβ42-induced delayed fibrinolysis in NHP. (D) Quantification of clot lysis rate in C. (E) Quantification of maximum clot turbidity in C. (C–E) Data from seven experiments, n = 7/group. (F) Representative scanning EM of clots formed from NHP with different treatments. (Scale bar, 5 µm.) (G and H) Analyses of scanning EM showing quantifications of fibrin diameter and total area of abnormal fibrin clumps/clusters. Data from three independent experiments. (I) Western blotting shows Aβ42+fibrinogen treatment reduced SYP and PSD-95 levels in OHC. However, in the presence of lecanemab, the Aβ42/fibrinogen-mediated reduction in PSD-95 and SYP was minimized. (J and K) Quantification of I. Data from four experiments. Changes in synaptic markers were not due to cell death as determined by propidium iodide staining. (L) B-Aβ42 was incubated in NHP to form complexes with fibrinogen. Lecanemab, aducanumab, buffer, or control IgG was added after 1 h. Western blot analysis of immunoprecipitation shows that lecanemab dissociated preformed Aβ42/fibrinogen complexes while aducanumab did not. (M) Quantification of L. Data from three independent experiments. (N) Western blotting shows treatment with preformed Aβ42/fibrinogen complexes reduced SYP and PSD-95 levels in OHC, but lecanemab mitigated this effect. (O and P) Quantification of SYP and PSD-95. Data from three independent experiments. Vehicle constitutes PBS+DMSO. Comparisons among multiple groups were performed using one-way ANOVA followed by Newman–Keuls multiple comparison test. Data are presented as mean ± SEM. ****P < 0.0001, ***P < 0.001, **P < 0.01; ns, not significant.