Increased N-terminal cleavage of alpha-2-antiplasmin in patients with liver cirrhosis

J Thromb Haemost. 2013 Nov;11(11):2029-36. doi: 10.1111/jth.12396.

Abstract

Background: The activity of alpha-2-antiplasmin (α2AP), the main fibrinolytic inhibitor, is modified by N- and C-terminal proteolytic cleavages. C-terminal cleavage converts plasminogen-binding α2AP (PB-α2AP) into a non-plasminogen-binding derivative. N-terminal cleavage by antiplasmin-cleaving enzyme (APCE), a soluble, circulating derivative of fibroblast activation protein (FAP), turns native Met-α2AP into Asn-α2AP, which is more quickly crosslinked into fibrin.

Objectives: We developed two novel enzyme-linked immunosorbent assays (ELISAs) to determine the N-terminal variation of α2AP to test the hypothesis that liver cirrhosis, characterized by increased expression of FAP/APCE, results in increased N-terminal cleavage of α2AP.

Patients/methods: α2AP and FAP/APCE antigen levels were measured in the plasma samples of 75 patients with cirrhosis with different severities and 30 healthy control individuals. The percentage of N-terminal cleavage of α2AP was calculated.

Results: Compared with levels (median [interquartile range]) in control individuals, total PB-α2AP levels and Met-PB-α2AP levels were reduced in cirrhosis patients (27.3 [21.4-41.3] μg mL(-1) vs. 56.2 [49.6-62.8] μg mL(-1) , P < 0.001, and 2.7 [1.7-5.5] μg mL(-1) vs. 12.1 [11.0-15.3] μg mL(-1) , P < 0.001, respectively). Interestingly, the percentage of N-terminal cleavage was increased in the patients (87.8 [85.0-91.6]% vs. 77.2 [72.2-79.8]% in controls, P < 0.001), as well as the plasma FAP/APCE levels (166 [60-550] ng mL(-1) in patients vs. 107 [67-157] ng mL(-1) in controls, P < 0.001). Additionally, all variables significantly correlated with the severity of disease.

Conclusions: Using our novel ELISAs we found increased N-terminal cleavage of α2AP in liver cirrhosis patients, which correlated with the severity of disease and is likely to have reflected the increased FAP/APCE levels in these patients.

Keywords: alpha-2-antiplasmin; case-control study; fibrinolysis; fibrosis; liver cirrhosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Antigens / chemistry
  • Case-Control Studies
  • Female
  • Fibrinolysis
  • Fibrosis / metabolism
  • Gelatinases / chemistry
  • Genotype
  • Humans
  • Liver Cirrhosis / blood*
  • Male
  • Membrane Proteins / chemistry
  • Middle Aged
  • Plasminogen / chemistry
  • Polymorphism, Single Nucleotide
  • Protein Binding
  • Protein Structure, Tertiary
  • Recombinant Proteins / chemistry
  • Serine Endopeptidases / chemistry
  • Solubility
  • Young Adult
  • alpha-2-Antiplasmin / chemistry*

Substances

  • Antigens
  • Membrane Proteins
  • Recombinant Proteins
  • alpha-2-Antiplasmin
  • Plasminogen
  • Serine Endopeptidases
  • fibroblast activation protein alpha
  • Gelatinases