Factor XIII Val34Leu mutation accelerates the development of fibrosis in patients with chronic hepatitis B and C

Transglutaminases in fibrosis-overview and recent advances

Transglutaminases (TGs) are a family of protein cross-linking enzymes that are capable of stiffening and insolubilizing proteins and creating protein networks, and thereby altering biological functions of proteins. Their role in fibrosis progression has been widely investigated with a focus on kidney, lung, liver, and heart where activity is triggered by various stimuli including hypoxia, inflammation, and hyperglycemia. TG2 has been considered one of the key enzymes in the pathogenesis of fibrosis mainly through transforming growth factor beta (TGF-beta) signaling and matrix cross-linking mechanisms. Although TG2 has been most widely studied in this context, the involvement of other TGs, TG1 and Factor XIII-A (FXIII-A), is beginning to emerge. This mini-review highlights the major steps taken in the TG and fibrosis research and summarizes the most recent advances and contributions of TG2, TG1, and FXIII-A to the progression of fibrosis in various animal models. Also, their mechanisms of action as well as therapeutic prospects are discussed.

Impact of prothrombin and factor V Leiden mutations on the progression of fibrosis in patients with chronic hepatitis C

Background

The role of thrombotic factors in the pathogenesis and progression of liver fibrosis remains obscure. We aimed to study the relationship between prothrombin G20210A (PT20210) and factor V Leiden (FVL) mutations and the progression of fibrosis and liver function in chronic HCV patients.

Methods

The study included 100 subjects, 88 patients with HCV-related cirrhosis (compensated: 38, decompensated: 50), and 12 controls. Patients with other viral hepatitis or coinfection, inherited metabolic disease, autoimmune hepatitis, hepatic or extrahepatic malignancy, in addition to patients with causes of hypoalbuminemia, elevated bilirubin or prolonged INR not related to cirrhosis were excluded from the study. Relevant clinical data were collected and basic laboratory tests were performed. Liver fibrosis was assessed using APRI and FIB-4 scores. FVL and PT20210 mutations were analyzed.

Results

FVL and PT20210 mutations were significantly higher in decompensated vs. compensated patients (32% vs. 5.3%, P = 0.001; 20% vs. 5.3%, 0.043, respectively) and absent in controls. Both mutations significantly correlated to the duration of infection, platelet count and fibrosis scores. PT20210 mutation significantly correlated to serum albumin and INR. Both mutations significantly predicted fibrosis scores, especially PT20210 (AUROC: 0.833 for APRI and 0.895 for FIB-4).

Conclusions

Both mutations are significantly correlated to fibrosis progression and liver profile and could be considered as markers predicting the need for early and different intervention.

[Role of polymorphic markers for the genes of hemostasis and platelet receptors in liver fibrosis progression in patients with chronic hepatitis C]

AIM

to estimate the clinical and prognostic value of the carriage of different allele variants of the gene polymorphisms of the coagulation system and platelet receptors in the progression of liver fibrosis (LF) in patient with chronic hepatitis C (CHC).

SUBJECTS AND METHODS

The investigation enrolled 177 patients with CHC and liver cirrhosis at its outcome who were divided into 2 groups according to the rate of LF progression: 1) 89 patients with rapid (rapid fibrosis) and 2) 88 patients with slow (slow fibrosis) progression. The polymorphism of the study genes was studied using a real-time polymerase chain reaction and a melting curve analysis.

RESULTS

In CHC patients, the FV 1691G/A genotype was more often in the rapid progressors than that in the slow progressors (10.11% vs 1.14%; p=0.011). The A allele of the 1691 G/A FV gene was more common in the rapid fibrosis group than that in the slow fibrosis group (1.7% vs 5.56%, odd ratio 9.787; p=0.139). In our investigation, the polymorphic marker GA in the FII 20210 G/A gene, as well as the 4G allele (5G4G + 4G4G genotypes) and the 4G allele of PAI-I -675 5G/4G were more often seen in the rapid fibrosis group than that in the slow fibrosis group; the detection rate was only at the trend level (p=0.118, p=0.112, and p=0.117 respectively). There were no significant differences between the groups in the spread of variant genotypes and alleles of other study genes. Integral model construction by coding «profibrogenic» genotypes (FV 1691 G/A, FII 20210 G/A, PAI-I -675 5G/4G) showed that the fibrosis progression rate expressed as fibrosis units annually also increased with higher total scores (p=0.039), indicating the combined effect of these genes.

CONCLUSION

The carriage of mutant genotypes of FV 1691 G/A, FII 20210 G/A, and PAI-I -675 5G/4G genes is a prognostic factor for rapid CHC progression.

Thrombin activation and liver inflammation in advanced hepatitis C virus infection

Hepatitis C virus (HCV) infection is associated with increased thrombotic risk. Several mechanisms are involved including direct endothelial damage by the HCV virus, with activation of tissue factor, altered fibrinolysis and increased platelet aggregation and activation. In advanced stages, chronic HCV infection may evolve to liver cirrhosis, a condition in which alterations in the portal microcirculation may also ultimately lead to thrombin activation, platelet aggregation, and clot formation. Therefore in advanced HCV liver disease there is an increased prevalence of thrombotic phenomena in portal vein radicles. Increased thrombin formation may activate hepatic stellate cells and promote liver fibrosis. In addition, ischemic changes derived from vascular occlusion by microthrombi favor the so called parenchymal extinction, a process that promotes collapse of hepatocytes and the formation of gross fibrous tracts. These reasons may explain why advanced HCV infection may evolve more rapidly to end-stage liver disease than other forms of cirrhosis.

Fibrin deposition following bile duct injury limits fibrosis through an αMβ2-dependent mechanism

Coagulation cascade activation and fibrin deposits have been implicated or observed in diverse forms of liver damage. Given that fibrin amplifies pathological inflammation in several diseases through the integrin receptor αMβ2, we tested the hypothesis that disruption of the fibrin(ogen)-αMβ2 interaction in Fibγ(390-396A) mice would reduce hepatic inflammation and fibrosis in an experimental setting of chemical liver injury. Contrary to our hypothesis, α-naphthylisothiocyanate (ANIT)-induced liver fibrosis increased in Fibγ(390-396A) mice, whereas inflammatory cytokine expression and hepatic necrosis were similar to ANIT-challenged wild-type (WT) mice. Increased fibrosis in Fibγ(390-396A) mice appeared to be independent of coagulation factor 13 (FXIII) transglutaminase, as ANIT challenge in FXIII-deficient mice resulted in a distinct pathological phenotype characterized by increased hepatic necrosis. Rather, bile duct proliferation underpinned the increased fibrosis in ANIT-exposed Fibγ(390-396A) mice. The mechanism of fibrin-mediated fibrosis was linked to interferon (IFN)γ induction of inducible nitric oxide synthase (iNOS), a gene linked to bile duct hyperplasia and liver fibrosis. Expression of iNOS messenger RNA was significantly increased in livers of ANIT-exposed Fibγ(390-396A) mice. Fibrin(ogen)-αMβ2 interaction inhibited iNOS induction in macrophages stimulated with IFNγ in vitro and ANIT-challenged IFNγ-deficient mice had reduced iNOS induction, bile duct hyperplasia, and liver fibrosis. Further, ANIT-induced iNOS expression, liver fibrosis, and bile duct hyperplasia were significantly reduced in WT mice administered leukadherin-1, a small molecule that allosterically enhances αMβ2-dependent cell adhesion to fibrin. These studies characterize a novel mechanism whereby the fibrin(ogen)-integrin-αMβ2 interaction reduces biliary fibrosis and suggests a novel putative therapeutic target for this difficult-to-treat fibrotic disease.