Hermann E. Wasmuth

Long‐term efficacy of tenofovir monotherapy for hepatitis B virus‐monoinfected patients after failure of nucleoside/nucleotide analogues

Tenofovir disoproxil fumarate (TDF) has demonstrated high antiviral efficacy in treatment‐naive patients with chronic hepatitis B virus (HBV) infection but experience in nucleoside/nucleotide analogue (NA)‐experienced patients is limited. In this retrospective multicenter study we therefore assessed the long‐term efficacy of TDF monotherapy in patients with prior failure or resistance to different NA treatments. Criteria for inclusion were HBV DNA levels >4.0 log10 copies/mL at the start and a minimum period of TDF therapy for at least 6 months. In all, 131 patients (mean age 42 ± 12 years, 95 male, 65% hepatitis B e antigen [HBeAg]‐positive) were eligible. Pretreatment consisted of either monotherapy with lamivudine (LAM; n = 18), adefovir (ADV; n = 8), and sequential LAM‐ADV therapy (n = 73), or add‐on combination therapy with both drugs (n = 29). Three patients had failed entecavir therapy. Resistance analysis in 113 of the 131 patients revealed genotypic LAM and ADV resistance in 62% and 19% of patients, respectively. The mean HBV DNA level at TDF baseline was 7.6 ± 1.5 log10 copies/mL. The overall cumulative proportion of patients achieving HBV DNA levels <400 copies/mL was 79% after a mean treatment duration of 23 months (range, 6–60). Although LAM resistance did not influence the antiviral efficacy of TDF, the presence of ADV resistance impaired TDF efficacy (100% versus 52% probability of HBV DNA <400 copies/mL, respectively). However, virologic breakthrough was not observed in any of the patients during the entire observation period. Loss of HBeAg occurred in 24% of patients and HBsAg loss occurred in 3%. No significant adverse events were noticed during TDF monotherapy. Conclusion: TDF monotherapy induced a potent and long‐lasting antiviral response in NA‐experienced patients with previous treatment failure. Our data may have implications for current add‐on strategies. (HEPATOLOGY 2009.)

Complement factor 5 is a quantitative trait gene that modifies liver fibrogenesis in mice and humans

Fibrogenesis or scarring of the liver is a common consequence of all chronic liver diseases. Here we refine a quantitative trait locus that confers susceptibility to hepatic fibrosis by in silico mapping and show, using congenic mice and transgenesis with recombined artificial chromosomes, that the gene Hc (encoding complement factor C5) underlies this locus. Small molecule inhibitors of the C5a receptor had antifibrotic effects in vivo, and common haplotype-tagging polymorphisms of the human gene C5 were associated with advanced fibrosis in chronic hepatitis C virus infection. Thus, the mouse quantitative trait gene led to the identification of an unknown gene underlying human susceptibility to liver fibrosis, supporting the idea that C5 has a causal role in fibrogenesis across species.

The fractalkine receptor CX3CR1 protects against liver fibrosis by controlling differentiation and survival of infiltrating hepatic monocytes

Chemokines modulate inflammatory responses that are prerequisites for organ fibrosis upon liver injury. Monocyte‐derived hepatic macrophages are critical for the development, maintenance, and resolution of hepatic fibrosis. The specific role of monocyte‐associated chemokine (C‐X3‐C motif) receptor 1 (CX3CR1) and its cognate ligand fractalkine [chemokine (C‐X3‐C motif) ligand 1)] in liver inflammation and fibrosis is currently unknown. We examined 169 patients with chronic liver diseases and 84 healthy controls; we found that CX3CL1 is significantly up‐regulated in the circulation upon disease progression, whereas CX3CR1 is down‐regulated intrahepatically in patients with advanced liver fibrosis or cirrhosis. To analyze the functional relevance of this pathway, two models of experimental liver fibrosis were applied to wild‐type (WT) and CX3CR1‐deficient mice. Fractalkine expression was induced upon liver injury in mice, primarily in hepatocytes and hepatic stellate cells. CX3CR1−/− animals developed greater hepatic fibrosis than WT animals with carbon tetrachloride–induced and bile duct ligation–induced fibrosis. CX3CR1−/− mice displayed significantly increased numbers of monocyte‐derived macrophages within the injured liver. Chimeric animals that underwent bone marrow transplantation revealed that CX3CR1 restricts hepatic fibrosis progression and monocyte accumulation through mechanisms exerted by infiltrating immune cells. In the absence of CX3CR1, intrahepatic monocytes develop preferentially into proinflammatory tumor necrosis factor–producing and inducible nitric oxide synthase–producing macrophages. CX3CR1 represents an essential survival signal for hepatic monocyte–derived macrophages by activating antiapoptotic bcl2 expression. Monocytes/macrophages lacking CX3CR1 undergo increased cell death after liver injury, which then perpetuates inflammation, promotes prolonged inflammatory monocyte infiltration into the liver, and results in enhanced liver fibrosis. Conclusion: CX3CR1 limits liver fibrosis in vivo by controlling the differentiation and survival of intrahepatic monocytes. The opposing regulation of CX3CR1 and fractalkine in patients suggests that pharmacological augmentation of this pathway may represent a possible therapeutic antifibrotic strategy. (HEPATOLOGY 2010;52:1769‐1782)

Antagonism of the chemokine Ccl5 ameliorates experimental liver fibrosis in mice

Activation of hepatic stellate cells in response to chronic inflammation represents a crucial step in the development of liver fibrosis. However, the molecules involved in the interaction between immune cells and stellate cells remain obscure. Herein, we identify the chemokine CCL5 (also known as RANTES), which is induced in murine and human liver after injury, as a central mediator of this interaction. First, we showed in patients with liver fibrosis that CCL5 haplotypes and intrahepatic CCL5 mRNA expression were associated with severe liver fibrosis. Consistent with this, we detected Ccl5 mRNA and CCL5 protein in 2 mouse models of liver fibrosis, induced by either injection of carbon tetrachloride (CCl4) or feeding on a methionine and choline-deficient (MCD) diet. In these models, Ccl5-/- mice exhibited decreased hepatic fibrosis, with reduced stellate cell activation and immune cell infiltration. Transplantation of Ccl5-deficient bone marrow into WT recipients attenuated liver fibrosis, identifying infiltrating hematopoietic cells as the main source of Ccl5. We then showed that treatment with the CCL5 receptor antagonist Met-CCL5 inhibited cultured stellate cell migration, proliferation, and chemokine and collagen secretion. Importantly, in vivo administration of Met-CCL5 greatly ameliorated liver fibrosis in mice and was able to accelerate fibrosis regression. Our results define a successful therapeutic approach to reduce experimental liver fibrosis by antagonizing Ccl5 receptors.

Antifibrotic Effects of CXCL9 and Its Receptor CXCR3 in Livers of Mice and Humans

BACKGROUND & AIMS Fibrosis is the hallmark of chronic liver diseases, yet many aspects of its mechanism remain to be defined. Chemokines are ubiquitous chemotactic molecules that mediate many acute and chronic inflammatory conditions, and CXC chemokine genes colocalize with a locus previously shown to include fibrogenic genes. We investigated the roles of the chemokine CXCL9 and its receptor CXCR3 in liver fibrosis. METHODS The effects of CXCL variants on fibrogenesis were analyzed using samples from patients with hepatitis C virus infection and by induction of fibrosis in CXCR3(-/-) and wild-type mice. In mice, intrahepatic immune cell subsets were investigated and interferon gamma messenger RNA levels were measured at baseline and after injury. Human serum CXCL9 levels were measured and correlated with CXCL9 variant and fibrosis severity. The effects of stimulation with CXCL9 were investigated on human hepatic stellate cells (LX-2). RESULTS Specific CXCL9 variants were associated with liver fibrosis in mice and humans; CXCL9 serum concentrations correlated with genotypes and levels of fibrosis in patients. In contrast to other chemokines, CXCL9 exerted antifibrotic effects in vitro, suppressing collagen production in LX-2 cells. CXCR3(-/-) mice had increased liver fibrosis; progression was associated with decreased numbers of intrahepatic interferon gamma-positive T cells and reduced interferon gamma messenger RNA, indicating that CXCL9-CXCR3 regulates Th1-associated immune pathways. CONCLUSIONS This is the first description of a chemokine-based antifibrotic pathway in the liver; antifibrotic therapies might be developed to modulate CXC chemokine levels.

Chemokines in Liver Inflammation and Fibrosis

Chemokines are a class of small chemotactic molecules with cytokine-like functions, which are well known to orchestrate inflammatory responses within different organs. Overall, more than 50 ligands and 19 receptors belong to the network. In recent years, accumulating functional and genetic evidence suggests that chemokines play a critical role in acute and chronic liver diseases, mediating the infiltration of immune cells (monocytes, T-cells) into the injured liver along a concentration gradient. However, chemokines can also directly affect the biology of liver resident cells, such as hepatic stellate cells and hepatocytes during inflammatory and fibrogenic tissue responses. Although the chemokine system has long been considered highly redundant, studies in knockout animals have convincingly demonstrated that single chemokines and chemokine receptors strongly affect the phenotype of toxic and inflammatory liver disease in vivo. However, depending on the model, these effects can be harmful (proinflammatory, profibrogenic) or beneficial (antifibrotic). This aspect of chemokine biology must be understood before these molecules and their receptors are targeted for therapeutic purposes. Here, we summarize current knowledge on the genetic and functional importance of the chemokine network in injury and highlight their potential for intervening in the inflammation and fibrosis that drives liver disease progression.

Intrahepatic cholestasis of pregnancy: the severe form is associated with common variants of the hepatobiliary phospholipid transporter ABCB4 gene

Background: Intrahepatic cholestasis of pregnancy (ICP) is characterised by troublesome maternal pruritus, raised serum bile acid levels and increased fetal risk. Mutations of the ABCB4 gene encoding the hepatobiliary phospholipid transporter have been identified in a small proportion of patients with cholestasis of pregnancy. In a recent prospective study on 693 patients with cholestasis of pregnancy, a cut-off level for serum bile acid (⩾40 μmol/l) was determined for increased risk of fetal complications. Objectives: To investigate whether common combinations of polymorphic alleles (haplotypes) of the genes encoding the hepatobiliary ATP-binding cassette (ABC) transporters for phospholipids (ABCB4) and bile acids (ABCB11) were associated with this severe form of cholestasis of pregnancy. Methods: For genetic analysis, 52 women with bile acid levels ⩾40 μmol/l (called cases) and 52 unaffected women (called controls) matched for age, parity and geographical residence were studied. Gene variants tagging common ABCB4 and ABCB11 haplotypes were genotyped and haplotype distributions were compared between cases and controls by permutation testing. Results: In contrast with ABCB11 haplotypes, ABCB4 haplotypes differed between the two groups (p = 0.019), showing that the severe form of cholestasis of pregnancy is associated with the ABCB4 gene variants. Specifically, haplotype ABCB4_5 occurred more often in cases, whereas haplotypes ABCB4_3 and ABCB4_7 were more common in controls. These associations were reflected by different frequencies of at-risk alleles of the two tagging polymorphisms (c.711A: odds ratio (OR) 2.27, p = 0.04; deletion intron 5: OR 14.68, p = 0.012). Conclusion: Variants of ABCB4 represent genetic risk factors for the severe form of ICP in Sweden.

CXC chemokine ligand 4 (Cxcl4) is a platelet‐derived mediator of experimental liver fibrosis

Liver fibrosis is a major cause of morbidity and mortality worldwide. Platelets are involved in liver damage, but the underlying molecular mechanisms remain elusive. Here, we investigate the platelet‐derived chemokine (C‐X‐C motif) ligand 4 (CXCL4) as a molecular mediator of fibrotic liver damage. Serum concentrations and intrahepatic messenger RNA of CXCL4 were measured in patients with chronic liver diseases and mice after toxic liver injury. Platelet aggregation in early fibrosis was determined by electron microscopy in patients and by immunohistochemistry in mice. Cxcl4−/− and wild‐type mice were subjected to two models of chronic liver injury (CCl4 and thioacetamide). The fibrotic phenotype was analyzed by histological, biochemical, and molecular analyses. Intrahepatic infiltration of immune cells was investigated by fluorescence‐activated cell sorting, and stellate cells were stimulated with recombinant Cxcl4 in vitro. The results showed that patients with advanced hepatitis C virus–induced fibrosis or nonalcoholic steatohepatitis had increased serum levels and intrahepatic CXCL4 messenger RNA concentrations. Platelets were found directly adjacent to collagen fibrils. The CCl4 and thioacetamide treatment led to an increase of hepatic Cxcl4 levels, platelet activation, and aggregation in early fibrosis in mice. Accordingly, genetic deletion of Cxcl4 in mice significantly reduced histological and biochemical liver damage in vivo, which was accompanied by changes in the expression of fibrosis‐related genes (Timp‐1 [tissue inhibitor of matrix metalloproteinase 1], Mmp9 [matrix metalloproteinase 9], Tgf‐β [transforming growth factor beta], IL10 [interleukin 10]). Functionally, Cxcl4−/− mice showed a strongly decreased infiltration of neutrophils (Ly6G) and CD8+ T cells into the liver. In vitro, recombinant murine Cxcl4 stimulated the proliferation, chemotaxis, and chemokine expression of hepatic stellate cells. Conclusion: The results underscore an important role of platelets in chronic liver damage and imply a new target for antifibrotic therapies. (HEPATOLOGY 2010.)

Chemokine-directed immune cell infiltration in acute and chronic liver disease.

The infiltration of various immune cell populations, including monocytes/macrophages, natural killer (NK), NKT cells and T cells, is a central pathogenic feature following acute- and chronic liver injury. Chemotactic cytokines, chemokines, are small-protein mediators that direct the migration of immune cells. Several hepatic cell populations, including hepatocytes, Kupffer cells, sinusoidal endothelial cells and hepatic stellate cells, can secrete chemokines upon activation. Samples from liver-disease patients and animal models of experimental injury highlight multiple activated chemokine pathways during initiation, maintenance or resolution of liver pathology. Monocyte chemoattractant protein-1 (Chemokine [C–C motif] ligand [CCL]2) can attract monocytes via CCR2. Infiltrating monocytes probably have functions in both disease progression and resolution of damage. RANTES (CCL5) may promote infiltration of NK (via CCR1) and T cells (via CCR5). Dissecting the exact functional contribution of immune cell subsets, chemokines and chemokine-receptor pathways in liver injury will hopefully identify novel targets for the treatment of acute liver failure, liver fibrosis or cirrhosis.

Chemokine Cxcl9 attenuates liver fibrosis‐associated angiogenesis in mice

Recent data suggest that the chemokine receptor CXCR3 is functionally involved in fibroproliferative disorders, including liver fibrosis. Neoangiogenesis is an important pathophysiological feature of liver scarring, but a functional role of angiostatic CXCR3 chemokines in this process is unclear. We therefore investigated neoangiogenesis in carbon tetrachloride (CCl4)‐induced liver fibrosis in Cxcr3−/− and wildtype mice by histological, molecular, and functional imaging methods. Furthermore, we assessed the direct role of vascular endothelial growth factor (VEGF) overexpression on liver angiogenesis and the fibroproliferative response using a Tet‐inducible bitransgenic mouse model. The feasibility of attenuation of angiogenesis and associated liver fibrosis by therapeutic treatment with the angiostatic chemokine Cxcl9 was systematically analyzed in vitro and in vivo. The results demonstrate that fibrosis progression in Cxcr3−/− mice was strongly linked to enhanced neoangiogenesis and VEGF/VEGFR2 expression compared with wildtype littermates. Systemic VEGF overexpression led to a fibrogenic response within the liver and was associated with a significantly increased Cxcl9 expression. In vitro, Cxcl9 displayed strong antiproliferative and antimigratory effects on VEGF‐stimulated endothelial cells and stellate cells by way of reduced VEGFR2 (KDR), phospholipase Cγ (PLCγ), and extracellular signal‐regulated kinase (ERK) phosphorylation, identifying this chemokine as a direct counter‐regulatory molecule of VEGF signaling within the liver. Accordingly, systemic administration of Cxcl9 led to a strong attenuation of neoangiogenesis and experimental liver fibrosis in vivo. Conclusion: The results identify direct angiostatic and antifibrotic effects of the Cxcr3 ligand Cxcl9 in a model of experimental liver fibrosis. The amelioration of liver damage by systemic application of Cxcl9 might offer a novel therapeutic approach for chronic liver diseases associated with increased neoangiogenesis. (HEPATOLOGY 2012)