Multiple variants in toll-like receptor 4 gene modulate risk of liver fibrosis in Caucasians with chronic hepatitis C infection

Toll-Like Receptor 4 Signaling in the Trabecular Meshwork

Primary open-angle glaucoma is one of the leading causes of blindness worldwide. With limited therapeutics targeting the pathogenesis at the trabecular meshwork (TM), there is a great need for identifying potential new targets. Recent evidence has implicated Toll-like receptor 4 (TLR4) and it is signaling pathway in augmenting the effects of transforming growth factor beta-2 (TGFβ2) and downstream extracellular matrix production. In this review, we examine the role of TLR4 signaling in the trabecular meshwork and the interplay between endogenous activators of TLR4 (damage-associated molecular patterns (DAMPs)), extracellular matrix (ECM), and the effect on intraocular pressure

Fibrosis and hepatic regeneration mechanism

Liver cirrhosis is the final stage of continuous hepatic inflammatory activity derived by viral, metabolic or autoimmune origin. In the last years, cirrhosis was considered a unique and static condition; recently was accepted some patients subgroups with different liver injury degrees that coexist under the same diagnosis, with implications about the natural disease history. The liver growth factor (LGF) is a potent in vivo and in vitro mitogenic agent and an inducer of hepatic regeneration (HR) through the hepatocytes DNA synthesis. The clinical implications of the LGF levels in cirrhosis, are not clear and even with having a fundamental role in the liver regeneration processes, the studies suggest that it could be a cirrhosis severity marker, in acute liver failure and in chronic hepatitis. Its role as predictor of mortality in fulminant hepatic insufficiency patients has been suggested. HR is one of the most enigmatic and fascinating biological phenomena. The rapid volume and liver function restoration after a major hepatectomy (>70%) or severe hepatocellular damage and its strict regulation of tissue damage response after the cessation, is an exclusive property of the liver. HR is the clinical applications fundament, such as extensive hepatic resections (>70% of the liver parenchyma), segmental transplantation or living donor transplantation, sequential hepatectomies, isolated portal embolization or associated with in situ hepatic transection, temporary artificial support in acute liver failure and the possible cell therapy clinical applications.

TRPM5 rs886277 Polymorphism Predicts Hepatic Fibrosis Progression in Non-Cirrhotic HCV-Infected Patients

BACKGROUND

TRPM5 (transient receptor potential cation channel subfamily M member 5) rs886277 polymorphism has been related to liver cirrhosis from different etiologies. The present study investigates the association of TRPM5 rs886277 polymorphism with liver fibrosis progression and cirrhosis development in chronic hepatitis C (CHC) patients.

METHODS

We conducted a retrospective study of 208 non-cirrhotic patients with CHC, who had at least two liver stiffness measurements (LSM) with a separation of 12 months (baseline LSM (LSM1) and the last LSM (LSM2)). Two outcome variables were considered: (1) LSM2/LSM1 ratio; (2) cirrhosis progression (F4; LSM ≥ 12.5 kPa). DNA genotyping was done at the CeGen using a MassARRAY platform.

RESULTS

The follow-up time was similar irrespective of the rs886277 genotype (46.4 months in TT genotype, 46.4 months in CT genotype, and 49.2 months in CC genotype; p = 0.649). The highest LSM increases were found in patients with CC genotype compared with TT and CT genotypes (p = 0.044 and p = 0.038, respectively). The cirrhosis progression was higher in patients with CC genotype than TT genotype (p = 0.033). Thus, the rs886277 C allele was associated with higher cirrhosis progression (adjusted odds ratio (aOR) = 2.64; p = 0.014). Moreover, rs886277 CC genotype was also related to higher values of LSM2/LSM1 ratio (adjusted arithmetic mean ratio a(AMR) = 1.31; p = 0.001) and cirrhosis progression (aOR = 4.33; p = 0.027).

CONCLUSIONS

TRPM5 rs886277 polymorphism was associated with liver fibrosis progression and cirrhosis development among hepatitis C virus (HCV)-infected patients. Specifically, the rs886277 C allele and CC genotype were risk factors for advancing liver fibrosis and cirrhosis compared to the rs886277 T allele and CT/TT genotype, respectively.

Staphylococcus aureus induces mammary gland fibrosis through activating the TLR/NF-κB and TLR/AP-1 signaling pathways in mice

To investigate the TLR-NF-κB/AP-1 pathways in S. aureus infection-induced mammary gland fibrosis, mice were infected with S. aureus isolated from the mammary glands of cows with mastitis. Lactating mice were divided into three groups: control group (CON); PBS control group (PBS) and the S. aureus-treated group (S. aureus). Pathological observations revealed that neutrophil infiltration into mammary gland tissue was obviously induced by S. aureus at the early stage of infection (1-7 d). With persistent S. aureus infection, mammary gland fibrosis developed and was characterized by infiltration and proliferation of macrophage, lymphocyte and fibroblast and ECM hyperplasia (7-21 d). Immunohistochemistry staining showed upregulation of fibrosis associated cytokines viz bFGF and PDGF-BB. Real-time qPCR and Western blot analysis revealed that transcription and translation of TLR2, TLR4, bFGF, PDGF-BB, α-SMA and COL Ⅰ α1 was significantly upregulated by S. aureus. NF-κB p65 and AP-I c-jun were translocated into the nucleus after S. aureus infection. There was no remarkable difference between the CON and PBS groups. The datas indicate that mammary gland fibrosis in mice is induced by S. aureus, which promotes cytokine release and the expression of ECM though activating the TLR/NF-κB p65 and TLR/AP-1 c-jun signaling pathways.

Fibronectin extra domain A (FN-EDA) elevates intraocular pressure through Toll-like receptor 4 signaling

Elevated intraocular pressure (IOP) is a major risk factor for the development and progression of primary open angle glaucoma and is due to trabecular meshwork (TM) damage, which leads to impaired aqueous humor outflow. Here, we explore a novel molecular mechanism involved in glaucomatous TM damage. We investigated the role of an endogenous Toll-like receptor 4 (TLR4) ligand, fibronectin-EDA (FN-EDA), in TGFβ2-induced ocular hypertension in mice. We utilized transgenic mouse strains that either constitutively express only FN containing the EDA isoform or contain an EDA-null allele and express only FN lacking EDA, with or without a mutation in Tlr4, in our inducible mouse model of ocular hypertension by injection of Ad5.TGFβ2. IOP was measured over time and eyes accessed by immunohistochemistry for total FN and FN-EDA expression. Constitutively active EDA caused elevated IOP starting at 14 weeks of age. Ad5.TGFβ2 induced ocular hypertension in wildtype C57BL/6J mice and further amplified the IOP in constitutively active EDA mice. TLR4 null and EDA null mice blocked Ad5.TGFβ-induced ocular hypertension. Total FN and FN-EDA isoform expression increased in response to Ad5.TGFβ2. These data suggest that both TLR4 and FN-EDA contribute to TGFβ2 induced ocular hypertension.

The associations between Toll-like receptor 4 gene polymorphisms and hepatitis C virus infection: a systematic review and meta-analysis

Background and objective: The hepatitis C virus (HCV) is able to cause a life-threatening disease relating to lethal hepatocellular carcinoma. Previous, Toll-like receptor polymorphisms were proposed as promising biomarker for HCV-related hepatocellular carcinoma and disease progression. This study aimed to summarize the association of TLR4 polymorphisms and HCV infection through meta-analysis.

Methods: We applied a systematic review and meta-analysis performed by using PubMed, EMBASE and Web of Science searches. The Modified Newcastle-Ottawa scale was used for quality assessment. The odd-ratio (OR) and 95% confidence interval (CI) were calculated to assess the association. In silico analysis was applied for proposing the function as microRNA (miRNA) of non-coding polymorphism. Finally, the miRNA target was predicted and annotated to suggest the possible relationship between polymorphism and HCV infection.

Results: Our meta-analysis incorporated seven studies involving rs4986791, rs4986790 and rs2149356. No association exists between rs4986791 and HCV infection. However, the heterozygous model (AG vs GG) of rs4986790 significantly associates with HCV infection (OR = 0.33, 95% CI = 0.21–0.49, P<0.0001). Moreover, the rs2149356 TG genotype also associates with HCV infection in the over-dominant model (TG vs TT+TG: OR = 0.54, 95% CI = 0.40–0.75). In silico analysis of rs2149356G allele showed that this mutation is siRNA, which targets the set of genes, especially in the autophagy pathway.

Conclusion: We demonstrated that rs4986790 and rs2149356 are associated with HCV infection.

Taurocholic acid is an active promoting factor, not just a biomarker of progression of liver cirrhosis: evidence from a human metabolomic study and in vitro experiments

BACKGROUND

Previous studies have indicated that bile acid is associated with progression of liver cirrhosis. However, the particular role of specific bile acid in the development of liver cirrhosis is not definite. The present study aims to identify the specific bile acid and explore its possible mechanisms in promoting liver cirrhosis.

METHODS

Thirty two cirrhotic patients and 27 healthy volunteers were enrolled. Age, gender, Child-Pugh classification and serum of patients and volunteers were collected. Liquid chromatography tandem mass spectrometry (LC-MS) was utilized to determine concentrations of 12 bile acids in serum. Principal component analysis, fold change analysis and heatmap analysis were used to identify the most changed bile acid. And pathway analysis was used to identify the most affected pathway in bile acid metabolism. Spearman rank correlation analysis was employed to assess correlation between concentrations of bile acids and Child-Pugh classification. Hepatic stellate cells (LX-2) were cultured in DMEM. LX-2 cells were also co-cultured with HepG2 cells in the transwell chambers. LX-2 cells were treated with Na+/taurocholate in different concentrations. Western blot was used to evaluate the expression of alpha smooth muscle actin (α-SMA), type I collagen, and Toll-like receptor 4 (TLR4) in LX-2 cells.

RESULTS

Concentrations of 12 bile acids in serum of patients and healthy volunteers were determined with LC-MS successively. Principal component analysis, fold change analysis and heatmap analysis identified taurocholic acid (TCA) to be the most changed bile acid. Pathway analysis showed that TCA biosynthesis increased significantly. Spearman rank correlation analysis showed that concentration of TCA in serum of cirrhotic patients was positively associated with Child-Pugh classification. TCA increased the expression of α-SMA, type I collagen, and TLR4 in LX-2 cells. Moreover, the above effect was strengthened when LX-2 cells were co-cultured with HepG2 cells.

CONCLUSIONS

Increased TCA concentration in serum of liver cirrhotic patients is mainly due to increased bile acid biosynthesis. TCA is an active promoter of the progression of liver cirrhosis. TCA promoting liver cirrhosis is likely through activating hepatic stellate cells via upregulating TLR4 expression. TCA is a potential therapeutic target for the prevention and treatment of liver cirrhosis.

Pharmacogenetics and the treatment of HIV-/HCV-coinfected patients

This review will summarize the role of pharmacogenetics in the natural history of hepatitis C, particularly in patients with HIV/HCV and will take the perspective of pharmacogenetics and its influence on the response to antiviral therapy and the susceptibility to develop adverse effects. This review will also devote a section to host genetics in other clinical situations, such as disease progression and acute HCV infection, which may determine whether treatment of HIV-/HCV-coinfected patients is implemented or deferred.

Proton pump inhibitors are associated with accelerated development of cirrhosis, hepatic decompensation and hepatocellular carcinoma in noncirrhotic patients with chronic hepatitis C infection: results from ERCHIVES

BACKGROUND

Proton pump inhibitors are among the most commonly prescribed medications in the United States. Their safety in cirrhosis has recently been questioned, but their overall effect on disease progression in noncirrhotic patients with chronic liver disease remains unclear.

AIM

To determine the impact of proton pump inhibitors on the progression of liver disease in noncirrhotic patients with hepatitis C virus (HCV) infection.

METHODS

Using the electronically retrieved cohort of HCV-infected veterans (ERCHIVES) database, we identified all subjects who received HCV treatment and all incident cases of cirrhosis, hepatic decompensation and hepatocellular carcinoma. Proton pump inhibitor use was measured using cumulative defined daily dose. Multivariate Cox regression analysis was performed after adjusting univariate predictors of cirrhosis and various indications for proton pump inhibitor use.

RESULTS

Among 11 526 eligible individuals, we found that exposure to proton pump inhibitors was independently associated with an increased risk of developing cirrhosis (hazard ratio [HR]: 1.32; 95% confidence interval: [1.17, 1.49]). This association remained robust to sensitivity analysis in which only patients who achieved sustained virologic response were analysed as well as analysis excluding those with alcohol abuse/dependence. Proton pump inhibitor exposure was also independently associated with an increased risk of hepatic decompensation (HR: 3.79 [2.58, 5.57]) and hepatocellular carcinoma (HR: 2.01 [1.50, 2.70]).

CONCLUSIONS

In patients with chronic HCV infection, increasing proton pump inhibitor use is associated with a dose-dependent risk of progression of chronic liver disease to cirrhosis, as well as an increased risk of hepatic decompensation and hepatocellular carcinoma.

Toll-like receptor 4 polymorphism as pretreatment predictor of response to HCV genotype 3a interferon-based treatment

Polymorphisms in Toll-like receptor 4 (TLR4) gene may exaggerate the chances and pathogenesis of HCV. Aim: This study intends to examine the relationship of genetic polymorphisms of TLR4 with HCV disease in Pakistani patients. Methodology: For this purpose, 500 blood samples were collected to confirm the genetic profile of all the subjects. Results: Single nucleotide polymorphism (SNP) in the TLR4 gene, rs4986790 (A>G), was genotyped in 400 HCV infected and 100 healthy individuals. The TLR4 gene was associated with a significantly increased risk of HCV-related diseases in comparing genotype assessments in patients and controls (pooled OR [95%CI]: 1.671 [0.946–2.949] for dominant; 0.503 [0.221–1.145] for recessive; 2.33 [1.518–3.576] for allele frequency). Subgroup analyses showed an increased risk of HCV infection and effect on interferon therapy associated with AA+AG/GG genotypes of rs4986790 (2.033 [1.094–3.778]). Conclusion: TLR4 SNP rs4986790 was found to be related to HCV-infected patients in the Pakistani population.

A896G and C1196T Polymorphisms Within the TLR4 Gene Abate Toll-Like Receptor 4-Mediated Signaling in HepG2 Cells

Toll-like receptor 4 (TLR4) appears to play an important role in the development and progression of hepatocellular carcinoma (HCC), but it is unclear whether single-nucleotide polymorphisms (SNPs) in the TLR4 gene influence HCC. In this study, we investigated the effects of TLR4 SNPs on HepG2 cell survival and proliferation, migration, and invasion. Plasmids carrying wild-type or mutant versions of the TLR4 gene (A896G and/or C1196T) were stably transfected into HepG2 cells, and cell viability and proliferation were analyzed using the Cell Counting Kit-8 (CCK-8) and 5-ethynyl-2'-deoxyuridine (EdU) incorporation assays, whereas apoptosis was assessed using flow cytometry. Migration and invasion were measured in a transwell chamber assay, and expression of inflammatory cytokines and downstream effectors was examined using real-time PCR and western blotting. Specific inhibitors of c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK), or phosphatidylinositol 3-kinase (PI3K) were added to the HepG2 cultures to explore the potential role of each pathway in TLR4 signaling. TLR4 SNPs did not affect expression levels in transfected cells. Compared with wild-type TLR4, mutant TLR4 was associated with lower cell proliferation, migration, invasion, and apoptotic threshold. In addition, the mutations were associated with significantly lower expression of nuclear factor κB (NF-κB), IL-6, and TGF-β1, even after stimulation with lipopolysaccharide. The expression of p-Akt was similar in the presence of wild-type or mutant TLR4. The 896G and 1196T SNPs in the TLR4 gene are associated with reduced TLR4-mediated signaling and, therefore, with lower survival, proliferation, and metastasis in HepG2 cells.

Crosstalk Between Transforming Growth Factor Beta-2 and Toll-Like Receptor 4 in the Trabecular Meshwork

Purpose

The trabecular meshwork (TM) is involved in the outflow of aqueous humor and intraocular pressure (IOP) regulation. Regulation of the extracellular matrix (ECM) by TGFβ2 signaling pathways in the TM has been extensively studied. Recent evidence has implicated toll-like receptor 4 (TLR4) in the regulation of ECM and fibrogenesis in liver, kidney, lung, and skin. Here, we investigated the role of TGFβ2-TLR4 signaling crosstalk in the regulation of the ECM in the TM and ocular hypertension.

Methods

Cross sections of human donor eyes, primary human TM cells in culture, and dissected mouse TM rings were used to determine Tlr4 expression in the TM. Trabecular meshwork cells in culture were treated with TGFβ2 (5 ng/mL), TLR4 inhibitor (TAK-242, 15 μM), and a TLR4 ligand (cellular fibronectin isoform [cFN]-EDA). A/J (n = 13), AKR/J (n = 7), BALBc/J (n = 8), C3H/HeJ (n = 20), and C3H/HeOuJ (n = 10) mice were injected intravitreally with adenovirus 5 (Ad5).hTGFβ2c226s/c228s in one eye, with the uninjected contralateral eye serving as a control. Conscious IOP measurements were taken using a TonoLab rebound tonometer.

Results

Toll-like receptor 4 is expressed in the human and mouse TM. Inhibition of TLR4 signaling in the presence of TGFβ2 decreases fibronectin expression. Activation of TLR4 by cFN-EDA in the presence of TGFβ2 further increases fibronectin, laminin, and collagen-1 expression, and TLR4 signaling inhibition blocks this effect. Ad5.hTGFβ2c226s/c228s induces ocular hypertension in wild-type mice but has no effect in Tlr4 mutant (C3H/HeJ) mice.

Conclusions

These studies identify TGFβ2-TLR4 crosstalk as a novel pathway involved in ECM regulation in the TM and ocular hypertension. These data further explain the complex mechanisms involved in the development of glaucomatous TM damage.

Frontline Science: HIV infection of Kupffer cells results in an amplified proinflammatory response to LPS

End-stage liver disease is a common cause of non-AIDS-related mortality in HIV+ patients, despite effective anti-retroviral therapies (ARTs). HIV-1 infection causes gut CD4 depletion and is thought to contribute to increased gut permeability, bacterial translocation, and immune activation. Microbial products drain from the gut into the liver via the portal vein where Kupffer cells (KCs), the resident liver macrophage, clear translocated microbial products. As bacterial translocation is implicated in fibrogenesis in HIV patients through unclear mechanisms, we tested the hypothesis that HIV infection of KCs alters their response to LPS in a TLR4-dependent manner. We showed that HIV-1 productively infected KCs, enhanced cell-surface TLR4 and CD14 expression, and increased IL-6 and TNF-α expression, which was blocked by a small molecule TLR4 inhibitor. Our study demonstrated that HIV infection sensitizes KCs to the proinflammatory effects of LPS in a TLR4-dependent manner. These findings suggest that HIV-1-infected KCs and their dysregulated innate immune response to LPS may play a role in hepatic inflammation and fibrosis and represent a novel target for therapy.

Risk Factors for Hepatocellular Carcinoma in Cirrhotic Patients with Chronic Hepatitis B

AIMS

To investigate the clinical and genetic risk factors associated with hepatocellular carcinoma (HCC) in cirrhotic patients with chronic hepatitis B (CHB).

METHODS

Nine hundred forty-nine Chinese Han patients with CHB were studied, including noncirrhotic patients without HCC (N = 234), cirrhotic patients without (N = 281) and with HCC (N = 434). Patients were genotyped for 10 candidate single nucleotide polymorphisms (SNPs) by the polymerase chain reaction (PCR)-ligase detection reaction (LDR) method.

RESULTS

By multivariate logistic regression analysis adjusted for Child-Pugh scores, noneffective antiviral treatment, drinking history, family history of HCC, and age ≥50 years old were associated with HCC risk (odds ratio [OR] = 5.923, 2.456, 2.241, 1.955, respectively). Sixty-two of 170 cirrhotic patients who achieved sustained virological suppression by antiviral treatment developed HCC, with fatty liver disease, family history of HCC, and family history of hepatitis B virus (HBV) infection as the risk factors (OR = 11.646, 3.339, 2.537, respectively). The SNPs associated with HCC risk in patients with cirrhosis and CHB were rs11536889 in TLR4 and rs2853744 in SPP1. Polymorphisms of TLR4 rs2149356, AP3S2 rs2290351, STXBP5L rs2169302, MLEC rs7976497, and SOCS3 rs4969168 were associated with HCC risk in specific stratified analyses with gender, age, and drinking history in the cirrhotic patients.

CONCLUSIONS

Inadequate antiviral treatment, family history of HCC, drinking history, and age ≥50 years old are risk factors for HCC. Sustained suppression of HBV does not eliminate the risk of HCC. Specific host genetic factors may impact HCC development in Han Chinese cirrhotic patients with CHB, including SNPs in TLR4, SPP1, AP3S2, STXBP5L, MLEC, and SOCS3, which warrant further validation in additional cohorts.

Rapidity of fibrosis progression in liver transplant recipients with recurrent hepatitis C is influenced by toll-like receptor 3 polymorphism

Liver transplantation activates the innate immune system through toll-like receptors (TLRs), potentially leading to allograft rejection and graft failure. We evaluated the association of single-nucleotide polymorphisms in TLR genes with the severity of hepatitis C virus recurrence after liver transplantation (LT). This is a two-center study of 176 adult patients who received a first LT from deceased donors for hepatitis C virus (HCV) cirrhosis. Eleven polymorphisms were evaluated by real-time polymerase chain reaction and melting curves analyses: TLR1 (Asp248Ser and Ser602Ile), TLR2 (Arg753Gln), TLR3 (Leu412Phe), TLR4 (Asp299Gly), TLR5 (Arg392Stop), TLR6 (Ser249Pro), TLR7 (Gln11Leu), TLR8 (Met1Val), and TLR9 (-1237T/C and -1486C/T). The CC genotype of TLR3 Leu412Phe in liver recipients was associated with severe recurrence (odds ratio (OR) = 2.01, 95% confidence interval (95% CI) = 1.02-3.93, p = 0.04). We also analyzed this polymorphism in 72 of their donors but no association was found with severity of HCV recurrence (p = 0.89). Multivariate analysis showed donor age older than 40 yr (OR=2.93; 95% CI = 1.49-5.8, p = 0.002) and the TLR3 Leu412Phe CC genotype (OR=2.02, 95%CI=1.01-4.05, p = 0.046) were independently associated with severe HCV recurrence. Our results show that the TLR3 Leu412Phe CC genotype is independently associated with severity of hepatitis C recurrence after LT.

Toll-like Receptor Expression and Signaling in Peripheral Blood Mononuclear Cells Correlate With Clinical Outcomes in Acute Hepatitis C Virus Infection

BACKGROUND

Mechanisms by which spontaneous clearance of acute hepatitis C occurs are unclear. A critical role for the innate immune system and IFNL4 polymorphisms has been proposed. This study investigates whether Toll-like receptor (TLR) expression and signaling during acute hepatitis C correlates with clinical outcomes.

METHODS

Participants identified from the Australian Trial in Acute Hepatitis C and the Networks study were followed longitudinally from the time of diagnosis of acute hepatitis C. Peripheral blood mononuclear cells (PBMCs) and plasma were collected at and 2 time points after diagnosis. At each time point, TLR2, TLR4, and CD86 expression on peripheral blood monocytes, natural killer (NK) cells, and NK T cells was measured, as well as the response of PBMCs to stimulation with TLR ligands. Cytokine and chemokine levels were measured in stimulated PBMCs and plasma.

RESULTS

We identified 20 participants with acute hepatitis C (10 with hepatitis C virus [HCV] monoinfection and 10 with HCV and human immunodeficiency virus coinfection). Eleven participants (55%) spontaneously cleared HCV. Acute hepatitis C and spontaneous clearance was associated with lower TLR4 expression on monocytes (P = .009) and NK cells (P = .029). Acute hepatitis C and spontaneous clearance was also associated with a reduced interferon γ response to TLR4 (P = .038) and TLR7/8 stimulation (P = .035), a reduced interleukin 6 response to TLR7/8 stimulation (P = .037), and reduced IFN-γ-inducible protein 10 (IP-10) response to TLR2 stimulation (P = .042). Lower plasma IP-10 levels were associated with spontaneous clearance (P = .001).

CONCLUSIONS

These findings implicate TLR4 signaling as playing a critical role in the outcome of acute hepatitis C.

Starring role of toll-like receptor-4 activation in the gut-liver axis

Since the introduction of the term “gut-liver axis”, many studies have focused on the functional links of intestinal microbiota, barrier function and immune responses to liver physiology. Intestinal and extra-intestinal diseases alter microbiota composition and lead to dysbiosis, which aggravates impaired intestinal barrier function via increased lipopolysaccharide translocation. The subsequent increased passage of gut-derived product from the intestinal lumen to the organ wall and bloodstream affects gut motility and liver biology. The activation of the toll-like receptor 4 (TLR-4) likely plays a key role in both cases. This review analyzed the most recent literature on the gut-liver axis, with a particular focus on the role of TLR-4 activation. Findings that linked liver disease with dysbiosis are evaluated, and links between dysbiosis and alterations of intestinal permeability and motility are discussed. We also examine the mechanisms of translocated gut bacteria and/or the bacterial product activation of liver inflammation and fibrogenesis via activity on different hepatic cell types.

Cellular and molecular functions of hepatic stellate cells in inflammatory responses and liver immunology

The liver is a central immunological organ. Liver resident macrophages, Kupffer cells (KC), but also sinusoidal endothelial cells, dendritic cells (DC) and other immune cells are involved in balancing immunity and tolerance against pathogens, commensals or food antigens. Hepatic stellate cells (HSCs) have been primarily characterized as the main effector cells in liver fibrosis, due to their capacity to transdifferentiate into collagen-producing myofibroblasts (MFB). More recent studies elucidated the fundamental role of HSC in liver immunology. HSC are not only the major storage site for dietary vitamin A (Vit A) (retinol, retinoic acid), which is essential for proper function of the immune system. This pericyte further represents a versatile source of many soluble immunological active factors including cytokines [e.g., interleukin 17 (IL-17)] and chemokines [C-C motif chemokine (ligand) 2 (CCL2)], may act as an antigen presenting cell (APC), and has autophagy activity. Additionally, it responds to many immunological triggers via toll-like receptors (TLR) (e.g., TLR4, TLR9) and transduces signals through pathways and mediators traditionally found in immune cells, including the Hedgehog (Hh) pathway or inflammasome activation. Overall, HSC promote rather immune-suppressive responses in homeostasis, like induction of regulatory T cells (Treg), T cell apoptosis (via B7-H1, PDL-1) or inhibition of cytotoxic CD8 T cells. In conditions of liver injury, HSC are important sensors of altered tissue integrity and initiators of innate immune cell activation. Vice versa, several immune cell subtypes interact directly or via soluble mediators with HSC. Such interactions include the mutual activation of HSC (towards MFB) and macrophages or pro-apoptotic signals from natural killer (NK), natural killer T (NKT) and gamma-delta T cells (γδ T-cells) on activated HSC. Current directions of research investigate the immune-modulating functions of HSC in the environment of liver tumors, cellular heterogeneity or interactions promoting HSC deactivation during resolution of liver fibrosis. Understanding the role of HSC as central regulators of liver immunology may lead to novel therapeutic strategies for chronic liver diseases.

Pathogenesis and prevention of hepatitis C virus-induced hepatocellular carcinoma

Hepatitis C virus (HCV) is one of the major aetiologic agents that causes hepatocellular carcinoma (HCC) by generating an inflammatory, fibrogenic, and carcinogenic tissue microenvironment in the liver. HCV-induced HCC is a rational target for cancer preventive intervention because of the clear-cut high-risk condition, cirrhosis, associated with high cancer incidence (1% to 7% per year). Studies have elucidated direct and indirect carcinogenic effects of HCV, which have in turn led to the identification of candidate HCC chemoprevention targets. Selective molecular targeted agents may enable personalized strategies for HCC chemoprevention. In addition, multiple experimental and epidemiological studies suggest the potential value of generic drugs or dietary supplements targeting inflammation, oxidant stress, or metabolic derangements as possible HCC chemopreventive agents. While the successful use of highly effective direct-acting antiviral agents will make important inroads into reducing long-term HCC risk, there will remain an important role for HCC chemoprevention even after viral cure, given the persistence of HCC risk in persons with advanced HCV fibrosis, as shown in recent studies. The successful development of cancer preventive therapies will be more challenging compared to cancer therapeutics because of the requirement for larger and longer clinical trials and the need for a safer toxicity profile given its use as a preventive agent. Molecular biomarkers to selectively identify high-risk population could help mitigate these challenges. Genome-wide, unbiased molecular characterization, high-throughput drug/gene screening, experimental model-based functional analysis, and systems-level in silico modelling are expected to complement each other to facilitate discovery of new HCC chemoprevention targets and therapies.

The association of toll-like receptor 4 polymorphism with hepatitis C virus infection in Saudi Arabian patients

Hepatitis C virus (HCV) is a single stranded RNA virus. It affects millions of people worldwide and is considered as a leading cause of liver diseases including cirrhosis and hepatocellular carcinoma. A recent study reported that TLR4 gene polymorphisms are good prognostic predictors and are associated with protection from liver fibrosis among Caucasians. This study aims to investigate the implication of genetic polymorphisms of TLR4 gene on the HCV infection in Saudi Arabian patients. Two SNPs in the TLR4 gene, rs4986790 (A/G) and rs4986791 (C/T), were genotyped in 450 HCV patients and 600 uninfected controls. The association analysis confirmed that both SNPs showed a significant difference in their distribution between HCV-infected patients and uninfected control subjects (P < 0.0001; OR = 0.404, 95% CI = 0.281-0.581) and (P < 0.0001; OR = 0.298, 95% CI = 0.201-0.443), respectively. More importantly, haplotype analysis revealed that four haplotypes, AC, GT, GC, and AT (rs4986790, rs4986791), were significantly associated with HCV infection when compared with control subjects. One haplotype AC was more prominently found when chronic HCV-infected patients were compared with cirrhosis/HCC patients (frequency = 94.7% and P = 0.04). Both TLR4 SNPs under investigation were found to be significantly implicated with HCV-infection among Saudi Arabian population.

Role of toll-like receptors in immune activation and tolerance in the liver

Liver has a unique vascular system receiving the majority of the blood supply from the gastrointestinal tract through the portal vein and faces continuous exposure to foreign pathogens and commensal bacterial products. These gut-derived antigens stimulate liver cells and result in a distinctive immune response via a family of pattern recognition receptors, the Toll-like receptors (TLRs). TLRs are expressed on Kupffer cells, dendritic cells, hepatic stellate cells, endothelial cells, and hepatocytes in the liver. The crosstalk between gut-derived antigens and TLRs on immune cells trigger a distinctive set of mechanisms to induce immunity, contributing to various acute and chronic liver diseases including liver cirrhosis and hepatocellular carcinoma. Accumulating evidence has shown that TLRs stimulation by foreign antigens induces the production of immunoactivating and immunoregulatory cytokines. Furthermore, the immunoregulatory arm of TLR stimulation can also control excessive tissue damage. With this knowledge at hand, it is important to clarify the dual role of disease-specific TLRs as activators and regulators, especially in the liver. We will review the current understanding of TLR signaling and subsequent immune activation and tolerance by the innate immune system in the liver.

Toll-like receptors and liver disease

Toll-like receptors (TLRs) are pattern recognition receptors that play an important role in host defence by recognizing pathogen-associated molecular patterns (PAMP). Recent studies indicate that TLR signalling plays an important role in progression of chronic liver diseases. Ongoing clinical trials suggest that therapeutic manipulation of TLR pathways may offer novel means of reversing chronic liver diseases. Upon activation by their respective ligands, TLRs initiate an intracellular pro-inflammatory/anti-inflammatory signalling cascade via recruitment of various adaptor proteins. TLR associated signalling pathways are tightly regulated to keep a check on inappropriate production of pro-inflammatory cytokines and interferons thereby preventing various autoimmune and inflammatory processes. Herein, we review the current state of knowledge of hepatic distribution, signalling pathways and therapeutic modulation of TLRs in chronic liver diseases.

TLR4 gene polymorphism in patients with nonalcoholic fatty liver disease in comparison to healthy controls

OBJECTIVES

Recent studies have suggested that bacterial overgrowth and endotoxemia along with its receptor, Toll-like receptor 4 (TLR-4), play a role in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). The present study was designed to test and evaluate the TLR4 gene polymorphism in patients with NAFLD in comparison to healthy controls.

METHODS

A total of 119 patients [mean (standard deviation, SD) age 43.4 (11.5) years, 55.5% were males] with NAFLD and 80 healthy controls [mean (SD) age 40.9 (8.1) years, 67.5% were females)] were evaluated in terms of patient demographics, anthropometrics, blood biochemistry, liver histology, and ultrasonographic (USG) findings. Histological evaluation was performed in 111 patients, and blood samples were collected from 119 patients with NAFLD and 80 healthy persons. Allelic variants of TLR4 (Asp299Gly and Thr399Ile) were assayed by real-time PCR. Genomic DNA was amplified using FAM/VIC primers specific for allelic variants of TLR4 Asp299Gly and Thr399Ile with real-time PCR. Amplicons were analyzed with high-resolution melting on a Light Cycler 480 for detecting different melting patterns of polymorphic and wild-type alleles.

RESULTS

The number of the subjects with heterozygous mutation at genotype 299 (Asp299Gly) was significantly lower in the NAFLD than in the control group (23.8 vs. 10.9%, P=0.027). Logistic regression analysis revealed that female gender [odds ratio (OR)=2.984, 95% confidence interval (CI) 1.561-5.360, P=0.001] and heterozygous (Asp299Gly) mutation at codon 299 (OR=2.998, 95% CI 1.325-6.783, P=0.008) were the significant predictors of higher likelihood of TRL4 gene polymorphism-related prevention of NAFLD.

CONCLUSIONS

As the first-time-in-humans controlled study related to investigation of TLR4 gene polymorphism in NAFLD, our findings contribute to the available data that TLR-4 signaling is pivotal for the pathogenesis of NASH and indicate that the TLR4 codon 299 heterozygous gene mutation (Asp299Gly) in humans may have a preventive role against the genesis of NAFLD.

Prediction of hepatic fibrosis in patients coinfected with HIV and hepatitis C virus based on genetic markers

OBJECTIVE

To assess the ability of the cirrhosis risk score (CRS) to predict liver fibrosis progression in HIV/hepatitis C virus (HCV)-coinfected patients.

DESIGN

Retrospective follow-up study.

METHODS

Based on a minimum follow-up time of 10 years with HCV infection, 190 HIV/HCV-coinfected patients were classified according to their METAVIR score: (1) 25 nonprogressor patients who did not develop fibrosis (F0) and (2) 165 progressor patients who developed fibrosis (F ≥ 1). Seven polymorphisms of CRS signature and IL28B genotype were performed using the GoldenGate assay. The CRS signature was calculated by naive Bayes formula as previously described.

RESULTS

Nonprogressors had CRS values significantly lower than progressors (0.61 versus 0.67; P = 0.043). Among the progressors, we observed similar CRS values through all the fibrosis stages (F1/F2/F3/F4). The percentage of patients with CRS > 0.70 (high risk of developing fibrosis) was higher in progressors than in nonprogressors; but the percentages with values between 0.50 and 0.70 (intermediate risk) and <0.50 (low risk) were quite similar for each of the fibrosis stages (P = 0.047). The area under the receiver-operating characteristic curve of CRS for discriminating nonprogressor versus progressor was 0.625 (P = 0.043). When clinical variables were considered (age at HCV infection, intravenous drug use, gender, IL28B, and HCV genotype), the area under the receiver-operating characteristic curve of CRS improved up to 0.739 (P < 0.001).

CONCLUSIONS

CRS itself seems not to be a good marker for identifying HIV/HCV-coinfected patients who are at high risk of developing liver fibrosis. However, CRS score coupled with clinical factors might help to distinguish between nonprogressors and progressors patients.

No correlation between PNPLA3 rs738409 genotype and fatty liver and hepatic cirrhosis in Japanese patients with HCV

Background

Hepatitis C virus (HCV) infection is associated with the development of cirrhosis and hepatocellular carcinoma and is also related to fatty change of the liver. Variation in patatin-like phospholipase domain-containing 3 (PNPLA3) gene is associated with disease progression in nonalcoholic fatty liver disease (NAFLD). Recent reports have suggested that PNPLA3, IL28B and TLR4-associated single nucleotide polymorphisms (SNPs) may have an impact on hepatic steatosis or fibrosis in patients with chronic HCV infection.

Methods and Findings

Four SNPs (PNPLA3 rs738409, TLR4 rs4986790, TLR4 rs4986791, IL28B rs8099917) were identified in Japanese patients infected with HCV. We examined the association between the distribution of these SNP alleles and fatty change of the liver or existence of hepatic cirrhosis diagnosed by ultrasonography, one of the widely accessible and easy-to-use methods. PNPLA3 rs738409 G-allele and IL28B rs 8099917 minor allele were found in 70.0% and 31.1%, respectively. These two TLR4 SNPs were uniform in Japanese. Fatty change of the liver developed independent of the abscence of hepatic cirrhosis on sonographic findings and younger age. Hepatic cirrhosis was associated with a higher aspartate aminotransferase/platelet ratio index (APRI), no fatty change of the liver, higher BMI and higher AFP levels. No association between PNPLA3 rs738409/IL28B rs8099917 genotypes and hepatic steatosis or liver fibrosis was observed.

Conclusions

According to ultrasound examinations, no association between PNPLA3 rs738409 genotype and fatty change of the liver or hepatic cirrhosis was found in Japanese patients infected with HCV. Together, our results suggested that the mechanism of hepatic steatosis underlying HCV infection might differ from that of NAFLD and should be explored.

No correlation between PNPLA3 rs738409 genotype and fatty liver and hepatic cirrhosis in Japanese patients with HCV

BACKGROUND

Hepatitis C virus (HCV) infection is associated with the development of cirrhosis and hepatocellular carcinoma and is also related to fatty change of the liver. Variation in patatin-like phospholipase domain-containing 3 (PNPLA3) gene is associated with disease progression in nonalcoholic fatty liver disease (NAFLD). Recent reports have suggested that PNPLA3, IL28B and TLR4-associated single nucleotide polymorphisms (SNPs) may have an impact on hepatic steatosis or fibrosis in patients with chronic HCV infection.

METHODS AND FINDINGS

Four SNPs (PNPLA3 rs738409, TLR4 rs4986790, TLR4 rs4986791, IL28B rs8099917) were identified in Japanese patients infected with HCV. We examined the association between the distribution of these SNP alleles and fatty change of the liver or existence of hepatic cirrhosis diagnosed by ultrasonography, one of the widely accessible and easy-to-use methods. PNPLA3 rs738409 G-allele and IL28B rs 8099917 minor allele were found in 70.0% and 31.1%, respectively. These two TLR4 SNPs were uniform in Japanese. Fatty change of the liver developed independent of the abscence of hepatic cirrhosis on sonographic findings and younger age. Hepatic cirrhosis was associated with a higher aspartate aminotransferase/platelet ratio index (APRI), no fatty change of the liver, higher BMI and higher AFP levels. No association between PNPLA3 rs738409/IL28B rs8099917 genotypes and hepatic steatosis or liver fibrosis was observed.

CONCLUSIONS

According to ultrasound examinations, no association between PNPLA3 rs738409 genotype and fatty change of the liver or hepatic cirrhosis was found in Japanese patients infected with HCV. Together, our results suggested that the mechanism of hepatic steatosis underlying HCV infection might differ from that of NAFLD and should be explored.

Regulation of wound healing and organ fibrosis by toll-like receptors

Chronic injury often triggers maladaptive wound healing responses leading to the development of tissue fibrosis and subsequent organ malfunction. Inflammation is a key component of the wound healing process and promotes the development of organ fibrosis. Here, we review the contribution of Toll-like receptors (TLRs) to wound healing with a particular focus on their role in liver, lung, kidney, skin and myocardial fibrosis. We discuss the role of TLRs on distinct cell populations that participate in the repair process following tissue injury, and the contribution of exogenous and endogenous TLR ligands to the wound healing response. Systemic review of the literature shows that TLRs promote tissue repair and fibrosis in many settings, albeit with profound differences between organs. In particular, TLRs exert a pronounced effect on fibrosis in organs with higher exposure to bacterial TLR ligands, such as the liver. Targeting TLR signaling at the ligand or receptor level may represent a novel strategy for the prevention of maladaptive wound healing and fibrosis in chronically injured organs. This article is part of a Special Issue entitled: Fibrosis: Translation of basic research to human disease.

Current and future therapies for hepatitis C virus infection

Only 20 years after the discovery of the Hepatitis C Virus (HCV), a cure is now likely for most people affected by this chronic infection, which carries a substantial disease burden, not only in the United States but also worldwide.1 The recent approval of two direct-acting antiviral agents that specifically inhibit viral replication has dramatically increased the viral clearance rate, from less than 10% with the initial regimen of interferon monotherapy to more than 70% with current therapy. Moreover, many other drugs targeting viral or host factors are in development, and some will almost certainly be approved in the coming years. The questions of who should be treated and with what regimen will be increasingly complex to address and will require careful consideration. As therapy improves, systemwide identification and care of patients who need treatment will be the next challenge. Because most infected persons are unaware of their diagnosis, the Centers for Disease Control and Prevention recently recommended screening for HCV all persons born between 1945 and 1965.2 ,3 It is anticipated that in the course of such a screening process, a large number of persons will be found to be infected with the virus; whether it will be possible to treat all these people is unclear. This article reviews the current therapy for HCV infection and the landscape of drug development.

Toll-like receptors in hepatitis C infection: implications for pathogenesis and treatment

Hepatitis C virus (HCV) infection is a significant global health problem, affecting over 150 million people worldwide. While the critical role of the adaptive immune system in HCV infection is well-established, the importance of the innate immune system in HCV infection has only been recognized in more recent years. Toll-like receptors form the cornerstone of the innate immune response, and there is considerable evidence for their crucial role in hepatitis C infection. This review outlines recent advances made in our understanding of the role of Toll-like receptor function in HCV infection, exploring how HCV manipulates host immunity to evade immune clearance and establish persistent infection despite leading to inflammatory hepatic damage.

Toll-like receptor-4 expression by hepatic progenitor cells and biliary epithelial cells in HCV-related chronic liver disease

Notwithstanding numerous evidences implicating toll-like receptor-4 (TLR4) in the pathogenesis of chronic hepatitis C virus (HCV) infection, the localization and level of TLR4 expression in the liver of patients with hepatitis C have never been investigated. We aimed to evaluate, by means of immunohistochemistry and real-time PCR (rt-PCR), hepatic TLR4 expression in patients with chronic HCV infection. Fifty patients who had undergone liver biopsy and 11 patients transplanted because of chronic HCV infection, and 12 controls free of liver disease, were included in the study. Each case was analyzed by immunohistochemistry for TLR4, α-smooth muscle actin and cytokeratin-7 (CK-7), and a subgroup of patients and all controls by rt-PCR for TLR4. Immunohistochemistry for α-smooth muscle actin was used to derive a score of activation of hepatic stellate cells and portal/septal myofibroblasts, while immunohistochemistry for CK-7 was used to evaluate and count hepatic progenitor cells, interlobular bile ducts and intermediate hepatocytes. In patients, the parenchymal elements responsible for the highest TLR4 level of expression were hepatic progenitor cells and biliary epithelial cells of interlobular bile ducts. Double-labeling experiments between anti-TLR4 and anti-CK7, anti-CD133, anti-CD44, anti-neural cell adhesion molecule, anti-epithelial cell adhesion molecule and anti-sex determining region Y-box 9, confirmed these findings. TLR4-positive hepatic progenitor cells and interlobular bile ducts were significantly correlated with the stage of liver disease (P<0.001), the grade of inflammation (P<0.001), and the activity of portal/septal myofibroblasts (P<0.001). rt-PCR study confirmed an increased TLR4 expression in the 26 patients analyzed with respect to controls (P<0.001). TLR4 expression positively correlated with fibrosis (P<0.05) and inflammation (P<0.05). The present results suggest that TLR4 expression by hepatic progenitor cells and biliary epithelial cells contributes to the progression of liver damage in the course of chronic HCV-related infection.

The phenotypic fate and functional role for bone marrow-derived stem cells in liver fibrosis

Liver fibrosis is an outcome of chronic liver injury of any etiology. It is manifested by extensive deposition of extracellular matrix (ECM) proteins that produce a fibrous scar in the injured liver. Bone marrow (BM) cells may play an important role in pathogenesis and resolution of liver fibrosis. BM cells contribute to the inflammatory response by TGF-β1 secretion and activation of liver resident myofibroblasts. Moreover, BM itself can serve as a source of collagen expressing cells, e.g. BM-derived fibrocytes and mesenchymal progenitors, which in turn, have a potential to in situ differentiate into fibrogenic myofibroblasts and facilitate fibrosis. Finally, BM cells play an active part in resolution of liver fibrosis after cessation of fibrogenic stimuli. While natural killer (NK) cells are implicated in apoptosis of activated hepatic stellate cells/myofibroblasts, cells of myelo-monocitic lineage secrete matrix metalloproteinases to actively degrade the fibrous scar. The focus of this review is on the current understanding of the role of different subsets of BM cells in the onset, development and resolution of liver fibrosis.

Increased hepatic expression of TLR2 and TLR4 in the hepatic inflammation-fibrosis-carcinoma sequence

We evaluated expression of TLR2, TLR4 and proinflammatory genes [NF-κB, TNF-α, cyclooxygenase-2 (COX-2)] in liver samples of patients in different stages of liver disease. Fifteen patients with unexplained transaminases elevation (reference group), 22 with viral chronic hepatitis (hepatitis group), 14 with virus-induced severe fibrosis/cirrhosis (cirrhosis group) and 10 with hepatocarcinoma (hepatocarcinoma group) were consecutively included in the study. Quantification of TLR2, TLR4, NF-κB, TNF-α and COX-2 mRNA was done by real-time RT-PCR and TLR2 and TLR4 protein expression was evaluated by immunohistochemistry. Compared with reference, TLR2 and TLR4 mRNA was increased in hepatitis (TLR2: 2.66 ± 0.69; TLR4: 3.11 ± 0.79; P < 0.05) and cirrhosis (TLR2: 2.14 ± 0.5; TLR4: 1.74 ± 0.27; P < 0.05) and decreased in hepatocarcinoma (TLR2: 0.48 ± 0.15; TLR4: 0.54 ± 0.10; P < 0.05). This associated with increased TNF-α and COX-2 mRNA in hepatitis (TNF-α: 3.24 ± 0.79; COX-2: 2.47 ± 0.36; P < 0.05) and cirrhosis (TNF-α: 1.73 ± 0.28; COX-2: 1.8 ± 0.35, P < 0.05), whereas NF-κB mRNA was increased in hepatitis (2.42 ± 0.31; P < 0.05) and unchanged in cirrhosis (1.34 ± 0.17; P = 0.3). Hepatocarcinoma presented increased COX-2 mRNA (1.63 ± 0.15; P < 0.05) and maintained (at decreased levels) mRNA of NF-κB (0.52 ± 0.12) and TNF-α (0.52 ± 0.12; P < 0.05, all genes). Immunohistochemistry confirmed increased expression of TLR2 and TLR4 in hepatitis and cirrhosis and maintained expression in hepatocarcinoma. Upregulation of TLR2, TLR4 and their proinflammatory mediators is associated with virus-induced hepatic IFC sequence.

Toll-like receptor 4 region genetic variants are associated with susceptibility to melioidosis

Melioidosis is a tropical infection caused by the Gram-negative soil saprophyte Burkholderia pseudomallei. Despite broad exposure of northeastern Thais, disease develops in only a small proportion of individuals. Although diabetes is a risk factor, the mechanisms of host susceptibility to melioidosis are still poorly understood. We postulated that Toll-like receptors (TLRs) regulate host susceptibility to disease, and that genetic variation in TLRs is associated with melioidosis. We analyzed the frequency of eight previously described TLR pathway polymorphisms in 490 cases compared with 950 non-hospitalized controls or 458 hospitalized controls. Based on these results, we then analyzed the frequency of additional TLR4 or TLR6-1-10 region polymorphisms in cases and controls. We found that the TLR4(1196C>T) variant was associated with protection from melioidosis when compared with non-hospitalized controls. The TLR1(742A>G) and TLR1(-7202A>G) variants were associated with melioidosis when compared with hospitalized controls. In further analyses, we found that two additional TLR4 region polymorphisms were associated with disease. In diabetics, three other TLR6-1-10 region polymorphisms were associated with disease when compared with hospitalized controls. We conclude that TLR genetic variants may modulate host susceptibility to melioidosis. Confirmation of these findings and further investigation of the mechanisms are required.

A polymorphism that delays fibrosis in hepatitis C promotes alternative splicing of AZIN1, reducing fibrogenesis

Among several single-nucleotide polymorphisms (SNPs) that correlate with fibrosis progression in chronic HCV, an SNP in the antizyme inhibitor (AzI) gene is most strongly associated with slow fibrosis progression. Our aim was to identify the mechanism(s) underlying this observation by exploring the impact of the AzI SNP on hepatic stellate cell (HSC) activity. Seven novel AZIN1 splice variants ("SV2-8") were cloned by polymerase chain reaction from the LX2 human HSC line. Expression of a minigene in LX2 containing the AZIN1 slow-fibrosis SNP yielded a 1.67-fold increase in AZIN1 splice variant 2 (AZIN1 SV2) messenger RNA (mRNA) (P = 0.05). In healthy human leukocytes, the SNP variant also correlated with significantly increased SV2 mRNA. Cells (293T) transfected with short hairpin RNA (shRNA) complementary to the exonic splicing chaperone SRp40 expressed 30% less SRp40 (P = 0.044) and 43% more AzI SV2 (P = 0.021) than control shRNA-expressing cells, mimicking the effect of the sequence variant. LX2 cells transfected with AZIN1 full-length complementary DNA expressed 35% less collagen I mRNA (P = 0.09) and 18% less α-smooth muscle actin mRNA (P = 0.09). Transient transfection of AZIN1 SV2 complementary DNA into LX2 cells reduced collagen I gene expression by 64% (P = 0.001) and α-smooth muscle actin by 43% (P = 0.005) compared to vector-transfected controls, paralleling changes in protein expression. Both AZIN1 and AZIN-SV2 mRNAs are detectable in normal human liver and reduced in HCV cirrhotic livers. The AZIN1-SV2 acts via a polyamine-independent pathway, as it neither interacts with antizyme nor affects the ability of AZIN1 lacking this variant to neutralize antizyme.

CONCLUSION

An SNP variant in the AZIN1 gene leads to enhanced generation of a novel alternative splice form that modifies the fibrogenic potential of HSCs.

Lack of an association between -308G>A polymorphism of the TNF-α gene and liver cirrhosis risk based on a meta-analysis

TNF-α is a potential proinflammatory cytokine that plays an important role in the pathogenesis of liver cirrhosis. We investigated a possible association between TNF-α -308G>A polymorphism and liver cirrhosis risk by conducting a meta-analysis. Publications addressing the association between TNF-α -308G>A and liver cirrhosis risk were selected from the Pubmed and Embase databases. Data were extracted from the studies by two independent reviewers; odds ratio (OR) with a 95% confidence interval (CI) was calculated from these data. The meta-analysis was performed by Review Manager Version 5.0.24 and STATA Version 9.2. Eleven studies were retrieved, reporting a total of 1796 liver cirrhosis cases and 2113 healthy controls. A meta-analysis of these 11 studies identified no significant association between TNF-α -308G>A polymorphism and liver cirrhosis risk in all comparisons of G vs A allele; GG vs GA + AA; GG + GA vs AA; GG vs AA; GG vs GA (OR = 1.14, 95%CI = 0.85-1.55, P = 0.38; OR = 1.24, 95%CI = 0.87- 1.77, P = 0.24; OR = 0.90, 95%CI = 0.62-1.30, P = 0.57; OR = 1.03, 95%CI = 0.56-1.89, P = 0.92; OR = 1.30, 95%CI = 0.90-1.88, P = 0.17; respectively). In conclusion, we found no association between TNF-α -308G>A polymorphism and liver cirrhosis risk, both in Caucasian and Asian populations.

Polymorphisms of toll-like receptors and their pathways in viral hepatitis

Toll-like receptors (TLRs) are an important part of the innate immune response to a variety of pathogens including hepatic viral infections. Activation of TLRs stimulates a complex intracellular signalling cascade that results in production of proinflammatory cytokines and interferons important for antiviral responses as well as induction of the adaptive arm of the immune system. There is substantial evidence for an important role for TLRs and TLR-mediated signalling in the pathogenesis and outcomes of hepatitis B and C in particular, but it might also influence responses to other viral hepatitis infections. Several single nucleotide polymorphisms (SNPs) of TLRs, relevant adaptor molecules and cytokines mediated by TLR signalling have been described that alter innate immune responses and have been implicated in a variety of human diseases including viral and other infections. There is now significant evidence that a number of TLR SNPs can affect various clinical outcomes in Caucasian patients with chronic HCV. However, the role of these polymorphisms in acute and other chronic hepatitis infections, including HBV as well as in non-Caucasian populations, has not been elucidated. In addition, results for SNPs downstream of TLR activation, such as in relevant cytokines, are inconsistent and their influence requires further investigation to determine the clinical significance of genetic variations in these mediators.

Hepatitis C Virus nonstructural 5A protein inhibits lipopolysaccharide-mediated apoptosis of hepatocytes by decreasing expression of Toll-like receptor 4

BACKGROUND

Hepatitis C virus (HCV) nonstructural protein 5A (NS5A) has been shown to modulate multiple cellular processes, including apoptosis. The aim of this study was to assess the effects of HCV NS5A on apoptosis induced by Toll-like receptor (TLR) 4 ligand, lipopolysaccharide (LPS).

METHODS

Apoptotic responses to TLR4 ligands and the expression of molecules involved in TLR signaling pathways in human hepatocytes were examined with or without expression of HCV NS5A.

RESULTS

HCV NS5A protected HepG2 hepatocytes against LPS-induced apoptosis, an effect linked to reduced TLR4 expression. A similar downregulation of TLR4 expression was observed in Huh-7-expressing genotype 1b and 2a. In agreement with these findings, NS5A inhibited the expression of numerous genes encoding for molecules involved in TLR4 signaling, such as CD14, MD-2, myeloid differentiation primary response gene 88, interferon regulatory factor 3, and nuclear factor-κB2. Consistent with a conferred prosurvival advantage, NS5A diminished the poly(adenosine diphosphate-ribose) polymerase cleavage and the activation of caspases 3, 7, 8, and 9 and increased the expression of anti-apoptotic molecules Bcl-2 and c-FLIP.

CONCLUSIONS

HCV NS5A downregulates TLR4 signaling and LPS-induced apoptotic pathways in human hepatocytes, suggesting that disruption of TLR4-mediated apoptosis may play a role in the pathogenesis of HCV infection.

Loss of CFTR affects biliary epithelium innate immunity and causes TLR4-NF-κB-mediated inflammatory response in mice

BACKGROUND & AIMS

Loss of function of the cystic fibrosis transmembrane conductance regulator (CFTR) in the biliary epithelium reduces bile flow and alkalinization in patients with cystic fibrosis (CF). Liver damage is believed to result from ductal cholestasis, but only 30% of patients with CF develop liver defects, indicating that another factor is involved. We studied the effects of CFTR deficiency on Toll-like receptor 4 (TLR4)-mediated responses of the biliary epithelium to endotoxins.

METHODS

Dextran sodium sulfate (DSS) was used to induce colitis in C57BL/6J-Cftrtm1Unc (Cftr-KO) mice and their wild-type littermates. Ductular reaction and portal inflammation were quantified by keratin-19 and CD45 immunolabeling. Cholangiocytes isolated from wild-type and Cftr-KO mice were challenged with lipopolysaccharide (LPS); cytokine secretion was quantified. Activation of nuclear factor κB (NF-κB), phosphorylation of TLR4, and activity of Src were determined. HEK-293 that expressed the secreted alkaline phosphatase reporter and human TLR4 were transfected with CFTR complementary DNAs.

RESULTS

DSS-induced colitis caused biliary damage and portal inflammation only in Cftr-KO mice. Biliary damage and inflammation were not attenuated by restoring biliary secretion with 24-nor-ursodeoxycholic acid but were significantly reduced by oral neomycin and polymyxin B, indicating a pathogenetic role of gut-derived bacterial products. Cftr-KO cholangiocytes incubated with LPS secreted significantly higher levels of cytokines regulated by TLR4 and NF-κB. LPS-mediated activation of NF-κB was blocked by the TLR4 inhibitor TAK-242. TLR4 phosphorylation by Src was significantly increased in Cftr-KO cholangiocytes. Expression of wild-type CFTR in the HEK293 cells stimulated with LPS reduced activation of NF-κB.

CONCLUSIONS

CFTR deficiency alters the innate immunity of the biliary epithelium and reduces its tolerance to endotoxin, resulting in an Src-dependent inflammatory response mediated by TLR4 and NF-κB. These findings might be used to develop therapies for CF-associated cholangiopathy.

Toll-like receptor signaling in liver regeneration, fibrosis and carcinogenesis

Toll-like receptors (TLR) are the germline-coded pattern recognition receptors that sense microbial products. This signaling orchestrates complex signaling pathways that induce expression of inflammatory genes for host defense against invading microorganisms. Recent studies illustrate the role of TLR on non-infectious inflammatory diseases. The liver has a unique anatomy bridging with the intestine by portal vein and bile ducts. This allows delivery of products from intestinal microflora directly into the liver. Subsequently, microbial products cause acute and chronic inflammation through TLR signaling in the liver. Not only exogenous products, but endogenous denatured products released from dying cells also facilitate inflammation even in sterile conditions. Consequently, these responses elicit tissue repairing including liver regeneration and fibrogenesis. An aberrant regenerative response may lead to hepatic carcinogenesis. In this review, we highlight the recently accumulated knowledge about TLR signaling in liver regeneration, fibrosis and carcinogenesis.

Liver fibrogenesis and genetic factors

Chronic liver diseases lead to the accumulation of fibrosis in the liver with eventual progression to cirrhosis and its complications. However, there is a wide range of inter-individual variation in the liver fibrogenesis process, thus posing a challenge to physicians to identify patients with poor prognosis. As demographic and environmental factors only account for a small portion of fibrogenesis variability, host genetic factors have been suggested as playing an important role. Due to technical limitations, the first genetic studies were restricted to the evaluation of candidate genes having a known or supposed function in liver fibrogenesis. Recently, technological improvements have made it possible to study the whole human genome in a single scan. Genome-wide association studies have considerably heightened the interest in genetics as part of the study of liver fibrogenesis through their identification of previously unsuspected genes that are statistically associated with liver fibrosis. It is thus possible to determine new diagnostic or prognostic genetic markers for the management of patients with chronic liver diseases. Moreover, functional analyses of these genes may provide new insights into the pathophysiology of liver fibrogenesis.

Explanted liver inflammatory grade predicts fibrosis progression in hepatitis C recurrence

Factors present prior to liver transplantation (LT) that predict fibrosis progression in recurrent hepatitis C infection (HCV) after LT would be important to identify. This study sought to determine if histologic grade of HCV in the explant predicts fibrosis progression in recurrent HCV. The clinical and histologic data of all 159 patients undergoing their first LT for HCV at our center from 1998 to 2001 were retrospectively reviewed with follow-up through June 2008. Twenty-five cases were excluded for: non-HCV-related graft loss <90 days (19), recidivism (4), or unavailable explant or follow-up biopsies (2). A single pathologist scored (Ishak) explants in a blinded fashion. Patients were grouped by explant inflammatory grade ≤ 4 (group1) and >4 (group 2). Prospectively scored liver biopsies (protocol months 1 and 4, annually, and as indicated clinically) were reviewed for development of advanced fibrosis (bridging or cirrhosis). Cox proportional hazard regression was used to analyze the association of explant grade, donor, viral and LT factors with progression to advanced fibrosis. The groups were well-matched for patient, viral, donor, and transplant factors. Five-year advanced fibrosis-free survival in group 1 versus group 2 was 63% versus 28%, P < 0.001. Explant grade >4 was associated with increased HCV-related graft loss at 1 (6% versus 3%) and 5 (36% versus 14%) years post-LT (P = 0.003). On univariate and multivariate Cox regression analysis, predictors of advanced fibrosis were explant grade >4 (hazard ratio [HR] = 3.3, 95% confidence interval [CI] = 1.9-5.6, P < 0.001) donor age >50 (HR = 3.3, 95% CI = 1.9-5.7, P < 0.001) and viral load at LT of >158,730 IU/mL (HR = 1.8, 95% CI = 1.05-3.1, P = 0.03).

CONCLUSION

Explant histologic grade can identify patients requiring more aggressive monitoring and intervention for HCV recurrence post-LT.

Genes and hepatitis C: susceptibility, fibrosis progression and response to treatment

Hepatitis C virus contact and infection show three different phenotypes: spontaneous viral clearance (SVC), chronic hepatitis C (CHC) and sustained virological response (SVR) following antiviral treatment. Many factors, including genetics, influence the evolution of these three phenotypes. We performed a literature search (PubMed) up to 31 January 2010 without language restriction to identify relevant studies on genes and hepatitis C. Additional studies were sought by reviewing the reference lists of the identified articles. Meta-analysis (using Meta-disk 1.4) was conducted to evaluate the association of single nucleotide polymorphism (SNP) in the IL28B region and SVR. The candidate gene approach showed strong relationships between human leucocyte antigen class II (DQB1(*) 0301 and DRB1(*) 1101) and SVC. A cirrhosis risk score involving 7 SNPs has been validated recently. The set of odds ratios of studies demonstrated an association between SNP (rs12987960/rs8099917) in the IL28B and SVR in CHC treated with peginterferon plus ribavirin (OR: 4.6; 95% CI: 2.9-7.3). The overall distribution of protective allele correlated with ethnic differences in SVR (Asians, Europeans, Hispanic and Afro-Americans) together with SVC, but not with fibrosis stage or viral load. These polymorphisms did not influence SVR in very-easy-to-treat patients such as genotype 2/3, rapid virological responders or patients with acute hepatitis C. While the genetic fingerprint for fibrosis progression remains elusive, IL28b polymorphism predicts SVC and SVR. However, nearly half of patients achieving SVR did not show favourable genotype. Further genetic signals are warranted to complete the puzzle of factors influencing hepatitis C.

Genetics and epigenetics in the fibrogenic evolution of chronic liver diseases

Recent years have seen unprecedented progress in the identification and characterization of genetic information related to chronic liver diseases (CLDs). However, despite the conceptual benefit in early recognition of at-risk populations amenable to pre-emptive treatment and/or surveillance strategies, recent genomic research in the field has placed focus on unravelling the genetic architecture of disease susceptibility, while data on genetic markers anticipating an accelerated fibrogenesis in an individual are still limited. Likewise, sequence variation assigning rapid fibrogenic evolution common to CLDs irrespective of etiology are poorly defined aside from PNPLA3 (adiponutrin) as a prominent exception. The emerging field of epigenetics in hepatology has mostly been studied under the perspective of gene regulation, less so as a heritable alteration in gene activity. In this article we will critically discuss recent findings in genomic hepatology with special focus on the (epi)genetic contribution to the fibrogenic evolution of CLDs.

Genetics of liver injury and fibrosis

Genetic risk factors play critical roles in liver injury and fibrosis, since both initiation and progression of chronic liver diseases differ between individuals challenged by identical environmental factors. Recently genomewide association studies have identified specific novel risk genes for (non-alcoholic) fatty liver disease (adiponutrin), viral hepatitis (interleukin 28B), and chronic cholestatic diseases (interleukin 12). Here, we summarize these studies and provide an inventory of the susceptibility genes. In the future, risk assessment of complex liver diseases might be based on polygenic risk scores or even gene networks. Complimentary to study in humans, experimental crosses of inbred mouse strains contribute to the genetic dissection of gene-gene interaction and gene-environment interactions. The results of these genomewide studies in mice and men might open new avenues for the prevention and treatment of chronic liver injury and the regression of liver fibrosis.

Toll-like receptors in innate immunity and infectious diseases

The protective ability of host defense system is largely dependent on germ-line encoded pattern-recognition receptors (PRRs). These PRRs respond to a variety of exogenous pathogens or endogenous danger signals, by recognizing some highly conserved structures such as pathogen-associated molecular patterns (PAMPs) and danger/damage associated molecular patterns (DAMPs). The most studied PRRs are Toll-like receptors (TLRs). Activation of TLRs triggers production of inflammatory cytokines and type I interferons (IFNs) via myeloid differentiation primary response gene 88 (MyD88)-dependent or -independent signaling respectively, thereby modulating innate and adaptive immunity, as well as inflammatory responses. This review introduces the classification, structure, and specific ligands of TLRs, and focuses on their signal pathways and biological activities, as well as clinical relevance. These studies of TLRs in the innate immune system have implications for the prevention and treatment of a variety of infectious diseases, including tuberculosis (TB), microbial keratitis, and hepatitis B and C.

Genome-wide association studies and genetic risk assessment of liver diseases

Genetic tests can help clinicians to diagnose rare monogenic liver diseases. For most common liver diseases, however, multiple gene variants that have small to moderate individual phenotypic effects contribute to the overall risk of disease. An individual's level of risk depends on interactions between environmental factors and a wide range of modifier genes, which are yet to be identified systematically. The latest genome-wide association studies in large cohorts of patients with gallstones, fatty liver disease, viral hepatitis, chronic cholestatic liver diseases or drug-induced liver injury have provided new insights into the pathophysiology of these illnesses and have suggested the contribution of previously unsuspected pathogenic pathways. Studies in mouse models have identified further susceptibility genes for several complex liver diseases. As a result, in the future polygenic risk scores might help to define subgroups of patients at risk of developing liver diseases who would benefit from preventative measures and/or personalized therapy. Now that whole-genome sequencing is possible, comprehensive strategies for integrating genomic data and counseling of patients need to be developed.