Summary
Plasma proteins mediate thrombogenesis, inflammation, endocardial injury and structural
remodelling in atrial fibrillation (AF). We hypothesised that anti-coagulation with
rivaroxaban, a direct factor Xa inhibitor, would differentially modulate biologically-relevant
plasma proteins, compared with warfarin, a multi-coagulation protein antagonist. We
performed unbiased liquid chromatography/tandem mass spectroscopy and candidate multiplexed
protein immunoassays among Japanese subjects with non-valvular chronic AF who were
randomly assigned to treatment with 24 weeks of rivaroxaban (n=93) or warfarin (n=94).
Nine metaproteins, including fibulin-1 (p=0.0033), vitronectin (p=0.0010), haemoglobin
α(p=0.0012), apolipoproteins C-II (p=0.0017) and H (p=0.0023), complement C5 precursor
(p=0.0026), coagulation factor XIIIA (p=0.0026) and XIIIB (p=0.0032) subunits, and
10 candidate proteins, including thrombomodulin (p=0.0004), intercellular adhesion
molecule-3 (p=0.0064), interleukin-8 (p=0.0007) and matrix metalloproteinase-3 (p=0.0003),
were differentially expressed among patients with and without known clinical risk
factors for stroke and bleeding in AF. Compared with warfarin, rivaroxaban treatment
was associated with a greater increase in thrombomodulin (Δ0.1 vs. 0.3 pg/ml, p=0.0026)
and a trend towards a reduction in matrix metalloproteinase-9 (Δ2.2 vs. –4.9 pg/ml,
p=0.0757) over 24 weeks. Only modest correlations were observed between protein levels
and prothrombin time, factor Xa activity and prothrombinase-induced clotting time.
Plasma proteomics can identify distinct functional patterns of protein expression
that report on known stroke and bleeding risk phenotypes in an ethnically-homogeneous
AF population. The greater upregulation of thrombomodulin among patients randomised
to rivaroxaban represents a proof-of-principle that pharmacoproteomics can be employed
to discern novel effects of factor Xa inhibition beyond standard pharmacodynamic measures.
Keywords
Atrial fibrillation - Proteomics - Thrombomodulin - warfarin and factor Xa inhibitor