Proapoptotic effects of the chemokine, CXCL 10 are mediated by the noncognate receptor TLR4 in hepatocytes.

UNLABELLED: Aberrant expression of the chemokine CXC chemokine ligand (CXCL)10 has been linked to the severity of hepatitis C virus (HCV)-induced liver injury, but the underlying molecular mechanisms remain unclear. In this study, we describe a yet-unknown proapoptotic effect of CXCL10 in hepatocytes, which is not mediated through its cognate chemokine receptor, but the lipopolysaccharide receptor Toll-like receptor 4 (TLR4). To this end, we investigated the link of CXCL10 expression with apoptosis in HCV-infected patients and in murine liver injury models. Mice were treated with CXCL10 or neutralizing antibody to systematically analyze effects on hepatocellular apoptosis in vivo. Direct proapoptotic functions of CXCL10 on different liver cell types were evaluated in detail in vitro. The results showed that CXCL10 expression was positively correlated with liver cell apoptosis in humans and mice. Neutralization of CXCL10 ameliorated concanavalin A-induced tissue injury in vivo, which was strongly associated with reduced liver cell apoptosis. In vitro, CXCL10 mediated the apoptosis of hepatocytes involving TLR4, but not CXC chemokine receptor 3 signaling. Specifically, CXCL10 induced long-term protein kinase B and Jun N-terminal kinase activation, leading to hepatocyte apoptosis by caspase-8, caspase-3, and p21-activated kinase 2 cleavage. Accordingly, systemic application of CXCL10 led to TLR4-induced liver cell apoptosis in vivo. CONCLUSION: The results identify CXCL10 and its noncognate receptor, TLR4, as a proapoptotic signaling cascade during liver injury. Antagonism of the CXCL10/TLR4 pathway might be a therapeutic option in liver diseases associated with increased apoptosis.

A 7-gene signature of the recipient predicts the progression of fibrosis after liver transplantation for hepatitis C virus infection.

Fibrosis recurrence after liver transplantation (LT) for hepatitis C virus (HCV) is a universal event and strongly determines a patient's prognosis. The recipient risk factors for fibrosis recurrence are still poorly defined. Here we assess a genetic risk score as a predictor of fibrosis after LT. The cirrhosis risk score (CRS), which comprises allele variants in 7 genes (adaptor-related protein complex 3 S2, aquaporin 2, antizyme inhibitor 1, degenerative spermatocyte homolog 1 lipid desaturase, syntaxin binding protein 5-like, toll-like receptor 4, and transient receptor potential cation channel M5), was calculated for 137 patients who underwent LT for HCV infection and experienced HCV reinfection of the graft. The patients were stratified into 3 CRS categories: <0.5, 0.5 to 0.7, and >0.7. All patients underwent protocol biopsy after LT (median follow-up = 5 years), and liver fibrosis was assessed according to the Desmet and Scheuer score. The data were analyzed with univariate and multivariate analyses. The results showed that the highest CRS category was strongly associated with the presence of F2 or F3 fibrosis in protocol biopsy samples 1, 3, and 5 years after LT (P = 0.006, P = 0.001, and P = 0.02, respectively). Overall, 75.0% of the patients with a CRS > 0.7 developed at least F2 fibrosis, whereas 51.5% developed F3 fibrosis during follow-up. The predictive value of the CRS for fibrosis progression was independent of known clinical risk factors, including the age of the donor, the sex of the recipient, and the occurrence of acute rejection. A Kaplan-Meier analysis confirmed the prognostic value of the CRS with respect to the recurrence of severe liver fibrosis in HCV-infected patients after LT (log rank = 6.23, P = 0.03). In conclusion, the genetic signature of the recipient predicts the likelihood of severe liver fibrosis in the graft after HCV recurrence. The CRS might help with early clinical decision making (eg, the selection of patients for antiviral therapy after LT).

Met-CCL5 modifies monocyte subpopulations during liver fibrosis regression.

Fibrosis or scarring of the liver parenchyma is a mainstay of chronic liver diseases and is associated with increased morbidity and mortality. Since complete scarring of the liver develops over several decades, therapeutic intervention with the aim of ameliorating fibrosis is of great clinical interest. In a recent study, we could identify the chemokine receptor antagonist Met-CCL5 as a potential compound to inhibit fibrosis progression and accelerate its regression. In the current study we characterized immune changes during fibrosis regression associated with the treatment with the CCL5 (RANTES) chemokine receptor antagonist Met-CCL5 in an established mouse model of chronic liver damage. Met-CCL5 or PBS was given after fibrosis induction (8 weeks of CCl(4)) and mice were sacrificed three and seven days after peak fibrosis. Mouse livers were analyzed for immune cell infiltration and cytokine gene expression. The results show that overall monocyte recruitment was not affected by Met-CCL5, but there was a significant shift to a pro-inflammatory Gr1+ monocyte population in the livers of mice treated with Met-CCL5. These monocytes were mostly iNOS +, a phenomenon which was also evident when analyzing the overall gene expression profiles in the livers. Since a shift in monocyte subpopulations has recently been identified to contribute to fibrosis regression, our results help explaining the efficacy of CCL5 chemokine antagonism as a novel treatment option for fibrotic liver diseases.