Angiopoietin-2 Serum Levels Improve Noninvasive Fibrosis Staging in Chronic Hepatitis C: A Fibrogenic-Angiogenic Link

Angiopoietin 2 levels decrease after HCV-cure and reflect the evolution of portal hypertension

BACKGROUND

Portal hypertension (PH) does not resolve in a considerable proportion of patients who achieved HCV-cure.

AIMS

To investigate (i)whether HCV-cure impacts cytokines that orchestrate angiogenesis (i.e.,Ang1/Ang2/VEGF) and fibrogenesis (i.e.,PDGF/TGF-β) and (ii)whether their changes reflect PH-evolution and its complications.

METHODS

We measured plasma levels of cytokines and von Willebrand factor (VWF) and assessed hepatic venous pressure gradient (HVPG) before/after HCV-cure in 66 patients with pre-treatment PH and 23 patients without advanced disease, who served as controls.

RESULTS

Following HCV-cure, we observed a decrease in Ang2/TGF-β, but no changes in the other cytokines. The differences in circulating cytokine profiles in PH patients persisted after removing the primary etiological factor. Patients with pre-treatment HVPG≥10 mmHg with HVPG-reduction≥10% had a more pronounced relative decrease in Ang2. Finally, post-treatment Ang2 predicted FU-HVPG≥16 mmHg/decompensation with AUROC-values of 0.804/0.835.

CONCLUSIONS

HCV-cure decreases circulating Ang2 - a mediator/indicator of dysangiogenesis/endothelial dysfunction, as well as TGF-β - a profibrogenic cytokine. The dynamics of Ang2 mirrored those of PH, rendering FU-Ang2 a non-invasive test for pronounced PH at FU that also predicts hepatic decompensation. The pathophysiological significance of the persistently altered cytokine levels for mechanisms that hinder the PH-regression warrants further study.

Angiopoietin-2 levels correlates with disease activity in children with nonalcoholic fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD), a chronic liver disease in children, ranges from nonalcoholic fatty liver (NAFL) to nonalcoholic steatohepatitis (NASH). We investigated the role of Angiopoietin-2 (Ang-2) as a biomarker for pediatric NAFLD-related liver damage.

METHODS

We assessed the plasma levels of Ang-2 and cytokeratin-18 (CK18) fragments and their association with histologic activity in 76 children with NAFLD and 28 controls.

RESULTS

The mean plasma levels of Ang-2 and CK18 were higher in children with NAFLD than in age-matched controls (Ang-2 155.4 ± 72.5 vs 7.5 ± 2.3 ng/mL, p < 0.001; CK18 390.4 ± 145.6 vs 193.9 ± 30.8 IU/L, p < 0.001). Ang-2 was significantly increased (p < 0.0001) in children with NASH (N = 41) while CK18 was significantly increased (p = 0.002) in children with fibrosis (N = 47). Ang-2 levels accurately predicted NASH (AUROC 0.911; 95% CI 0.844-0.979; p < 0.0001), while CK18 predicted both NASH (AUROC 0.827; 95% CI 0.735-0.919; p < 0.0001) and fibrosis (AUROC 0.724; 95% CI 0.611-0.837; p = 0.001). Ang-2 and CK18 in combination were good predictors of NASH with a sensitivity of 71.4% and a specificity of 100%.

CONCLUSIONS

In conclusion, our data suggested Ang-2 as a suitable biomarker of NASH in the pediatric population. However, our findings need external validation in other cohorts.

IMPACT

Several circulating factors have been extensively studied as potential biomarkers for NASH. Angiopoietin-2 circulating levels are increased in children with NAFLD and are associated with NASH. Angiopoietin-2 levels are more efficient than CK18 levels at assessing the most severe form of disease, and the combining of these two biomarkers reached a positive predictive value of 100% for NASH.

Angiopoietin-2 as a predictor of fibrosis regression in chronic hepatitis C virus patients after direct-acting antiviral drugs

Background

HCV infection is a major health concern. Disease progression to fibrosis, cirrhosis, and HCC is aided by the persistence of inflammatory reactions and cellular damage. Moreover, angiogenesis was found to have a substantial pathogenic role in disease progression. Serum Angiopoietin-2 appears to be correlated with liver stiffness in chronic HCV and its elevation is linked to disease progression from chronic hepatitis to cirrhosis. The aim of this study was to evaluate the role of serum Angiopoietin-2 in the prediction of regression of fibrosis in chronic HCV patients receiving direct-acting antiviral agents. Forty Egyptian chronic HCV patients for whom direct-acting antiviral agent (DAA) therapy was planned were included. All patients underwent assessment twice, at baseline and at SVR12, for standard laboratory tests, measurement of fibrosis using FibroScan, FIB-4 and APRI scores, and Angiopoietin-2 level.

Results

Statistically significantly higher levels of baseline Ang-2 were detected with the progression of fibrosis stages with a p-value of <0.001. The best cutoff value of baseline Ang-2 in discrimination of liver cirrhosis (F4) from F0-F3 was > 630 pg/ml with 85.71% sensitivity and 84.85% specificity. A statistically significant decline of Ang-2 (from 464.3±237.2 pg/ml to 401.3±277.1 pg/ml) was noted after the achievement of SVR12 with a p-value < 0.001. Regression of liver fibrosis in this study is defined as a decrease of more than or equal to one stage in liver fibrosis. Lower baseline fibrosis stages and other non-invasive scoring systems (FIB-4 and APRI scores) were associated with regression of fibrosis following successful DAAs treatment. However, higher baseline Ang-2 levels were significantly associated with non-regression of fibrosis, and at a cutoff of >680 pg/ml, it might predict non-regression of fibrosis after successful eradication of HCV with DAAs with 93.33% sensitivity and 70% specificity.

Conclusions

Angiopoietin-2 can be a useful predictor of fibrosis regression in chronic HCV patients receiving direct-acting antiviral agents. Elevated baseline Angiopoietin-2 and advanced fibrosis stages may predict non-regression of liver fibrosis.

Serum Angiopoietin-2 Predicts Mortality and Kidney Outcomes in Decompensated Cirrhosis

Acute kidney injury in decompensated cirrhosis has limited therapeutic options, and novel mechanistic targets are urgently needed. Angiopoietin-2 is a context-specific antagonist of Tie2, a receptor that signals vascular quiescence. Considering the prominence of vascular destabilization in decompensated cirrhosis, we evaluated Angiopoietin-2 to predict clinical outcomes. Serum Angiopoietin-2 was measured serially in a prospective cohort of hospitalized patients with decompensated cirrhosis and acute kidney injury. Clinical characteristics and outcomes were examined over a 90-day period and analyzed according to Angiopoietin-2 levels. Primary outcome was 90-day mortality. Our study included 191 inpatients (median Angiopoietin-2 level 18.2 [interquartile range 11.8, 26.5] ng/mL). Median Model for End-Stage Liver Disease (MELD) score was 23 [17, 30] and 90-day mortality was 41%. Increased Angiopoietin-2 levels were associated with increased mortality (died 21.9 [13.9, 30.3] ng/mL vs. alive 15.2 [9.8, 23.0] ng/mL; P < 0.001), higher Acute Kidney Injury Network stage (stage I 13.4 [9.8, 20.1] ng/mL vs. stage II 20.0 [14.1, 26.2] ng/mL vs. stage III 21.9 [13.0, 29.5] ng/mL; P = 0.002), and need for renal replacement therapy (16.5 [11.3, 23.6] ng/mL vs. 25.1 [13.3, 30.3] ng/mL; P = 0.005). The association between Angiopoietin-2 and mortality was significant in unadjusted and adjusted Cox regression models (P ≤ 0.001 for all models), and improved discrimination for mortality when added to MELD score (integrated discrimination increment 0.067; P = 0.001). Conclusion: Angiopoietin-2 was associated with mortality and other clinically relevant outcomes in a cohort of patients with decompensated cirrhosis with acute kidney injury. Further experimental study of Angiopoietin/Tie2 signaling is warranted to explore its potential mechanistic and therapeutic role in this population.

Intrahepatic angiopoietin-2 correlates with chronic hepatitis C progression and is induced in hepatitis C virus replicon systems

BACKGROUND & AIMS

Chronic hepatitis C (CHC) is a major cause of cirrhosis and hepatocellular carcinoma and angiogenesis is closely related to the pathogenesis and progression of different chronic liver diseases (CLD). Thus, the intrahepatic expression of angiopoietins 1 and 2 (Ang1 and Ang2), as relevant mediators of pathological angiogenesis in several CLD, was investigated. In addition, the differential influence of structural and non-structural genomic regions of HCV on the expression of angiopoietins and the possible signalling involved were studied.

METHODS

Ang1 and Ang2 expression was evaluated by western blotting and enzyme-linked immunosorbent assay (ELISA) in liver homogenates of CHC patients (n=47) and uninfected subjects (n=8). Their association with disease progression (according to METAVIR classification) was assessed by Spearman's correlation. Statistical differences among the expression of angiopoietins at different CHC stages were calculated by Mann-Whitney U-test. Finally, the in vitro expression of Angiopoietins in HCV replicons (complete or non-structural subgenomic) and the main signalling pathways involved were also examined.

RESULTS

Ang2 levels were significantly higher in the liver of CHC patients compared to controls and significantly correlated with inflammation and fibrosis. Accordingly, an increased expression of Ang2 was found in all HCV replicons tested. Interestingly, the inhibition of MEK and PI3K signalling pathways exerted differential effects on Ang2 expression concerning to the genomic region of HCV.

CONCLUSIONS

Hepatitis C virus induces Ang2 expression in hepatocytes through different signalling routes which may lead to the disregulation of vascular homeostasis in the liver. Thus, pharmacologic intervention on Ang2 signalling might constitute an important therapeutic tool.

Therapeutic targeting of the angiopoietin-TIE pathway

The endothelial angiopoietin (ANG)-TIE growth factor receptor pathway regulates vascular permeability and pathological vascular remodelling during inflammation, tumour angiogenesis and metastasis. Drugs that target the ANG-TIE pathway are in clinical development for oncological and ophthalmological applications. The aim is to complement current vascular endothelial growth factor (VEGF)-based anti-angiogenic therapies in cancer, wet age-related macular degeneration and macular oedema. The unique function of the ANG-TIE pathway in vascular stabilization also renders this pathway an attractive target in sepsis, organ transplantation, atherosclerosis and vascular complications of diabetes. This Review covers key aspects of the function of the ANG-TIE pathway in vascular disease and describes the recent development of novel therapeutics that target this pathway.

Angiopoietin-2/angiopoietin-1 as non-invasive biomarker of cirrhosis in chronic hepatitis C

AIM

To evaluate the efficacy of peripheral blood concentrations of angiopoietins (Ang) as cirrhosis biomarkers of chronic hepatitis C (CHC).

METHODS

Ang1 and Ang2 serum levels were measured by enzyme-linked immunosorbent assays (ELISA) in samples from 179 cirrhotic and non-cirrhotic CHC patients, classified according to the METAVIR system. Groups were compared by non-parametric Mann-Whitney U test. Subsequently, the association of peripheral concentrations of angiopoietins with the stage of fibrosis was analyzed using Spearman correlation test. Finally, the accuracy, sensitivity and specificity of circulating angiopoietins for cirrhosis diagnosis were determined by the study of the respective area under the curve of receiver operator characteristics (AUC-ROC).

RESULTS

Peripheral blood concentrations of Ang1 and Ang2 in CHC patients were significantly related to fibrosis. While Ang1 was decreased in cirrhotic subjects compared to non-cirrhotic (P < 0.0001), Ang2 was significantly increased as CHC progressed to the end stage of liver disease (P < 0.0001). Consequently, Ang2/Ang1 ratio was notably amplified and significantly correlated with fibrosis (P < 0.0001). Interestingly, the individual performance of each angiopoietin for the diagnosis of cirrhosis reached notable AUC-ROC values (above 0.7, both), but the Ang2/Ang1 ratio was much better (AUC-ROC = 0.810) and displayed outstanding values of sensitivity (71%), specificity (84%) and accuracy (82.1%) at the optimal cut-off (10.33). Furthermore, Ang2/Ang1 ratio improved the performance of many other previously described biomarkers or scores of liver cirrhosis in CHC.

CONCLUSION

Ang2/Ang1 ratio might constitute a useful tool for monitoring the progression of chronic liver disease towards cirrhosis and play an important role as therapeutic target.

Inhibition of tyrosine kinase receptor Tie2 reverts HCV-induced hepatic stellate cell activation

Background

Hepatitis C virus (HCV) infection is a major cause of chronic liver disease (CLD) and is frequently linked to intrahepatic microvascular disorders. Activation of hepatic stellate cells (HSC) is a central event in liver damage, due to their contribution to hepatic renewal and to the development of fibrosis and hepatocarcinoma. During the progression of CLDs, HSC attempt to restore injured tissue by stimulating repair processes, such as fibrosis and angiogenesis. Because HSC express the key vascular receptor Tie2, among other angiogenic receptors and mediators, we analyzed its involvement in the development of CLD.

Methods

Tie2 expression was monitored in HSC cultures that were exposed to media from HCV-expressing cells (replicons). The effects of Tie2 blockade on HSC activation by either neutralizing antibody or specific signaling inhibitors were also examined.

Results

Media from HCV-replicons enhanced HSC activation and invasion and upregulated Tie2 expression. Notably, the blockade of Tie2 receptor (by a specific neutralizing antibody) or signaling (by selective AKT and MAPK inhibitors) significantly reduced alpha-smooth muscle actin (α-SMA) expression and the invasive potential of HCV-conditioned HSC.

Conclusions

These findings ascribe a novel profibrogenic function to Tie2 receptor in the progression of chronic hepatitis C, highlighting the significance of its dysregulation in the evolution of CLDs and its potential as a novel therapeutic target.