Mechanisms of Disease: HCV-induced liver injury

Effect of combined siRNA of HCV E2 gene and HCV receptors against HCV

Background/Aim

Hepatitis C virus (HCV) is a major threat as almost 3% of the world's population (350 million individual) and 10% of the Pakistani population is chronically infected with this virus. RNA interference (RNAi), a sequence-specific degradation process of RNA, has potential to be used as a powerful alternative molecular therapeutic approach in spite of the current therapy of interferon-α and ribavirin against HCV which has limited efficiency. HCV structural gene E2 is mainly involved in viral cell entry via attachment with the host cell surface receptors i.e., CD81 tetraspanin, low density lipoprotein receptor (LDLR), scavenger receptor class B type 1 (SR-B1), and Claudin1 (CLDN1). Considering the importance of HCV E2 gene and cellular receptors in virus infection and silencing effects of RNAi, the current study was designed to target the cellular and viral factors as new therapeutic options in limiting HCV infection.

Results

In this study the potential of siRNAs to inhibit HCV-3a replication in serum-infected Huh-7 cells was investigated by combined treatment of siRNAs against the HCV E2 gene and HCV cellular receptors (CD81 and LDLR), which resulted in a significant decrease in HCV viral copy number.

Conclusion

From the current study it is concluded that the combined RNAi-mediated silencing of HCV E2 and HCV receptors is important for the development of effective siRNA-based therapeutic option against HCV-3a.

microRNAs: Fad or future of liver disease

microRNAs (miRs) are small non-coding RNAs that regulate both mRNA and protein expression of target genes, which results in alterations in mRNA stability or translation inhibition. miRs influence at least one third of all human transcripts and are known regulators of various important cellular growth and differentiation factors. miRs have recently emerged as key regulatory molecules in chronic liver disease. This review details recent contributions to the field of miRs that influence liver development and the broad spectrum of disease, from non-alcoholic fatty liver disease to fibrosis/cirrhosis, with particular emphasis on hepatic stellate cells and potential use of miRs as therapeutic tools.

Effect of antiviral therapy on the immunohistochemical expression of bcl-xL and bax protein in patients with HBeAg-negative chronic hepatitis B

The effect of antiviral treatment on apoptosis in chronic hepatitis B (CHB) has not been clarified. We evaluated the hepatic immunohistochemical expression of the pro-apoptotic bax and the antiapoptotic bcl-xL protein in HBeAg-negative CHB patients before and after treatment. In our study we included 72 paired biopsies from 36 HBeAg-negative CHB patients: 29 treated (interferon-alfa: 17, adefovir: 12) and 7 untreated. Changes in expression of apoptotic proteins (D-bax, D-bcl-xL), necroinflammation and fibrosis (D-grade/D-stage) (Ishak classification) were evaluated. We found that Bax-positive compared to bax-negative biopsies had worse necroinflammation (8.2 vs. 6.7, P = 0.05) and fibrosis score (3.9 vs. 3, P = 0.036). bcl-xL-positive compared to bcl-xL-negative biopsies had lower intralobular inflammation (1.6 vs. 2.2, P = 0.03). Decreased compared to stable/increased D-bax was associated with greater improvement in necroinflammation only in treated patients (D-grade: -4.6 vs. -1.6, P = 0.05) and greater fibrosis improvement in interferon treated patients (D-stage: -0.4 vs. 0.55, P = 0.05). Increased compared to stable/decreased total apoptotic trend [D-apoptosis: (D-bax)-(D-bcl-xL)], was associated with worsening fibrosis, particularly in adefovir treated patients (D-stage: 2.3 vs. 0, P = 0.004). In the 11 patients without significant changes from 1st to 2nd biopsy, increased apoptosis was more frequent in treated than untreated cases (P = 0.046). In multivariate analysis, bax change was independently associated with change of grade (P = 0.038) and antiviral therapy (P = 0.015). In conclusions, in HBeAg-negative CHB, histological improvement after treatment is associated with decreased hepatocyte apoptosis. In patients without substantial histological changes, treatment seems to increase the apoptosis of hepatocytes, thus having a possible protective effect on hepatocarcinogenesis.

Perspectives on fibrosis progression in hepatitis C: an à la carte approach to risk factors and staging of fibrosis

The morbidity and mortality of chronic hepatitis C is related to progressive fibrosis and the development of cirrhosis. The development of fibrosis in patients with HCV is highly influenced by immune status, host response to the virus and associated factors, such as, age, sex, alcohol intake, diabetes, obesity and coinfection with other viruses. The rate of fibrosis progression differs depending on several factors, including the stage of fibrosis and the time since infection. Routine assessment of fibrosis through biopsy every 3-5 years has poor patient acceptance and reliability, and might result in missed opportunities to improve or modify treatment priorities. Enhanced understanding of the pathophysiology of liver fibrosis in HCV infection has led to the development of a number of non-invasive assessment modalities. The ideal test would discriminate fibrosis in the categories none/early (stages 0/1), intermediate (stage 2) and advanced fibrosis/cirrhosis (stages 3/4) and be readily available, inexpensive and accurate. Biomarker tests utilize individual or combined serum markers to determine the degree of fibrosis. Other strategies combine biomarkers with clinical variables, such as patient age or utilize liver imaging or functional assessments. Incorporation of appropriately validated non-invasive assessments of liver fibrosis will likely improve the clinical care of patients with HCV infection.

Hepatic stellate cells and fibrogenesis in hepatitis C virus infection: an ultrastructural insight

An ultrastructural quantitative assessment of hepatic stellate cells (HSCs) was made in relation to hepatic fibrosis, apoptotic cellular changes, intracellular fat deposition, circulating inflammatory cells in the sinusoids, and the necroinflammatory activity in liver specimens of 33 patients proven to be positive for hepatitis C virus (HCV)-RNA by polymerase chain reaction with the intention that electron microscopy may throw more light on the role of HSCs in the complicated process of fibrogenesis. A detailed review concerning these parameters and observed evidence suggesting the potential properties of HSCs to recycle cellular debris into collagen fibers are reported.

A crucial role for Kupffer cell-derived galectin-9 in regulation of T cell immunity in hepatitis C infection

Approximately 200 million people throughout the world are infected with hepatitis C virus (HCV). One of the most striking features of HCV infection is its high propensity to establish persistence (approximately 70-80%) and progressive liver injury. Galectins are evolutionarily conserved glycan-binding proteins with diverse roles in innate and adaptive immune responses. Here, we demonstrate that galectin-9, the natural ligand for the T cell immunoglobulin domain and mucin domain protein 3 (Tim-3), circulates at very high levels in the serum and its hepatic expression (particularly on Kupffer cells) is significantly increased in patients with chronic HCV as compared to normal controls. Galectin-9 production from monocytes and macrophages is induced by IFN-gamma, which has been shown to be elevated in chronic HCV infection. In turn, galectin-9 induces pro-inflammatory cytokines in liver-derived and peripheral mononuclear cells; galectin-9 also induces anti-inflammatory cytokines from peripheral but not hepatic mononuclear cells. Galectin-9 results in expansion of CD4(+)CD25(+)FoxP3(+)CD127(low) regulatory T cells, contraction of CD4(+) effector T cells, and apoptosis of HCV-specific CTLs. In conclusion, galectin-9 production by Kupffer cells links the innate and adaptive immune response, providing a potential novel immunotherapeutic target in this common viral infection.

A crucial role for Kupffer cell-derived galectin-9 in regulation of T cell immunity in hepatitis C infection

Approximately 200 million people throughout the world are infected with hepatitis C virus (HCV). One of the most striking features of HCV infection is its high propensity to establish persistence (∼70–80%) and progressive liver injury. Galectins are evolutionarily conserved glycan-binding proteins with diverse roles in innate and adaptive immune responses. Here, we demonstrate that galectin-9, the natural ligand for the T cell immunoglobulin domain and mucin domain protein 3 (Tim-3), circulates at very high levels in the serum and its hepatic expression (particularly on Kupffer cells) is significantly increased in patients with chronic HCV as compared to normal controls. Galectin-9 production from monocytes and macrophages is induced by IFN-γ, which has been shown to be elevated in chronic HCV infection. In turn, galectin-9 induces pro-inflammatory cytokines in liver-derived and peripheral mononuclear cells; galectin-9 also induces anti-inflammatory cytokines from peripheral but not hepatic mononuclear cells. Galectin-9 results in expansion of CD4⁺CD25⁺FoxP3⁺CD127^low regulatory T cells, contraction of CD4⁺ effector T cells, and apoptosis of HCV-specific CTLs. In conclusion, galectin-9 production by Kupffer cells links the innate and adaptive immune response, providing a potential novel immunotherapeutic target in this common viral infection.

Adverse outcomes in Alaska natives who recovered from or have chronic hepatitis C infection

BACKGROUND & AIMS

The factors associated with adverse outcome from hepatitis C virus (HCV) infection are incompletely understood. To determine the incidence and risk factors associated with the development of end-stage liver disease (ESLD) and liver-related death (LRD), we conducted a retrospective/prospective population-based study in a cohort of Alaska Native persons chronically infected with HCV from 1994 to 2005.

METHODS

We followed 960 persons prospectively for an average of 7.2 years and retrospectively for 12.1 years with data from medical records and serum samples. We compared data from subjects that were chronically infected with those who recovered from HCV infection, stratified by alcohol use. Survival models were used to examine factors associated with ESLD and LRD in chronically infected patients.

RESULTS

During prospective follow-up, 80 (8.8%) and 47 (5.2%) patients developed ESLD and LRD, respectively. In examining incidence per 100 person-years, no difference was found among heavy alcohol users in the incidence of LRD (2.28 versus 3.50; P = .34) or ESLD (3.21 versus 5.69; P = .13) in persons with chronic HCV compared with those recovered from HCV infection. In subjects that consumed <50 g alcohol/d, the incidences of LRD were 0.77 and 0.09 (P = .01) and of ESLD were 1.58 versus 0.36 (P = .002), respectively, in subjects with chronic infection versus those that recovered. Multivariate analysis showed that older age, heavy alcohol use, and HCV genotype 3 were associated with ESLD.

CONCLUSIONS

A history of heavy alcohol use is associated with the highest incidence of LRD and ESLD, regardless of whether patients are chronically infected or recover from HCV infection.

Chronic hepatitis C--assessment in civil law: a case study

This article describes the case of a 58-year-old man who asked for an assessment of physical damage of a civil nature, having been diagnosed with chronic hepatitis C for which he blamed a blood transfusion, supposedly contaminated with hepatitis C virus (HCV). After studying the documentary information, a number of presuppositions were drawn up with a view to determining the causal nexus, but this could not be proved. The assessment of situations like this is not common in civil law. This article is intended to add to the body of information on the forensic assessment of similar cases.

Complete blood count, measures of iron status and inflammatory markers in inner-city African Americans with undiagnosed hepatitis C seropositivity

BACKGROUND

Hepatitis C virus (HCV) infection may be associated with thrombocytopenia and increased iron stores in patients receiving medical care. We aimed to determine how often changes in hematologic, iron metabolic and inflammatory markers occur in individuals with undiagnosed HCV in the community.

METHODS

Inner-city African Americans (n=143) were recruited from the community according to reported ingestion of alcohol. They were divided broadly into those who drank more or less than 56 g alcohol/day as assessed by dietary questionnaire. HCV serology was determined and laboratory values were compared according to HCV seropositivity in analyses that adjusted for alcohol consumption.

RESULTS

The prevalence of HCV seropositivity was 23% among men and 29% among women. Levels of hepatocellular enzymes were higher with HCV seropositivity (P<0.0001) but hemoglobin concentrations, white blood cell and platelet counts and serum ferritin concentrations did not differ. The globulin fraction of the serum protein concentration (P=0.002) was increased with HCV seropositivity as expected with chronic inflammation. However, erythrocyte sedimentation rate and serum iron and haptoglobin levels did not differ significantly according to HCV status. Furthermore, multivariate analysis revealed that C-reactive protein was decreased and transferrin concentration was increased with both HCV and alcohol consumption (P<0.014).

CONCLUSIONS

Previously undiagnosed HCV seropositivity has little effect on the complete blood count and body iron stores but appears to perturb the response to an inflammatory stimulus, causing reduced rather than increased circulating CRP concentrations and increased rather than decreased transferrin concentrations.

Evolution of hepatitis C virus in liver allografts

1. Hepatitis C virus (HCV) RNA+ liver allograft recipients invariably reinfect the liver allograft within hours after transplantation, and the majority (>70%) develop chronic hepatitis. The rate at which these patients experience progression to cirrhosis and the overall percentage are significantly increased in comparison with HCV infection in the nontransplant setting. 2. Core needle biopsy evaluation is used to establish the diagnosis of recurrent HCV, which can be difficult to distinguish from acute cellular rejection and other causes of allograft dysfunction. In the vast majority of cases, however, distinguishing recurrent HCV from other posttransplant syndromes is reliably achieved by a careful examination of hematoxylin and eosin-stained sections and correlation with clinical and serological data. 3. Recurrent HCV often coexists with other causes of liver allograft dysfunction, and the determination of the most important cause of injury and whether other causes of injury are present is important. Included are residual changes of preservation/reperfusion injury, biliary sludging/structuring, acute cellular and chronic rejection, and autoimmune hepatitis. 4. The complex interplay between immunosuppression management, viral replication, and the recipient immune system results in distinct patterns of recurrent chronic HCV in the liver allograft: (1) conventional or usual acute and chronic HCV, which resembles that seen in the general population with HCV; (2) fibrosing cholestatic hepatitis; and (3) plasma cell-rich HCV, which might represent a variant of, or overlap with, autoimmune hepatitis and rejection. 5. The variable but usually hastened histopathological progression toward cirrhosis in HCV+ allografts is similar to that seen in the nontransplant setting, but in allografts, the overall severity of lymphocytic inflammation is less, and ductular reactions, stellate cell activation, and subsinusoidal fibrosis are accentuated. Hepatic stressors and causes of an impaired ability of hepatocytes to replicate include persistently high levels of viral replication, HCV-specific CD4+ T responses, advanced donor age, high levels or rapid withdrawal of immunosuppression, and coexistent liver damage from preservation/reperfusion injury, biliary structuring, or coexistent cytomegalovirus or herpes 6 viral infection. 6. Immunological effector mechanisms involved in the rejection and control of HCV replication/HCV elimination show significant overlap. Patients with very high levels of HCV RNA rarely show significant clinically significant acute or chronic rejection, whereas their occurrence is frequently associated with very low levels or clearance of HCV RNA. Studying the evolution from recurrent HCV to acute rejection in patients treated with interferon and/or weaned from immunosuppression might provide valuable insights into the relationship between these 2 processes as well as liver allograft acceptance.

Hepatitis C virus (HCV) proteins induce NADPH oxidase 4 expression in a transforming growth factor beta-dependent manner: a new contributor to HCV-induced oxidative stress

Viral hepatitis-induced oxidative stress accompanied by increased levels of transforming growth factor beta (TGF-beta) and hepatic fibrosis are hallmarks of hepatitis C virus (HCV) infection. The mechanisms of redox regulation in the pathogenesis of HCV-induced liver disease are not clearly understood. The results of our current studies suggest that reactive oxygen species (ROS) derived from Nox4, a member of the NADPH oxidase (Nox) family, could play a role in HCV-induced liver disease. We found that the expression of HCV (genotype 1a) cDNA constructs (full-length and subgenomic), core protein alone, viral RNA, or replicating HCV (JFH-AM2) induced Nox4 mRNA expression and ROS generation in human hepatocyte cell lines (Huh-7, Huh-7.5, HepG2, and CHL). Conversely, hepatocytes expressing Nox4 short hairpin RNA (shRNA) or an inactive dominant negative form of Nox4 showed decreased ROS production when cells were transfected with HCV. The promoters of both human and murine Nox4 were used to demonstrate transcriptional regulation of Nox4 mRNA by HCV, and a luciferase reporter tied to an approximately 2-kb promoter region of Nox4 identified HCV-responsive regulatory regions modulating the expression of Nox4. Furthermore, the human Nox4 promoter was responsive to TGF-beta1, and the HCV core-dependent induction of Nox4 was blocked by antibody against TGF-beta or the expression of dominant negative TGF-beta receptor type II. These findings identified HCV as a regulator of Nox4 gene expression and subsequent ROS production through an autocrine TGF-beta-dependent mechanism. Collectively, these data provide evidence that HCV-induced Nox4 contributes to ROS production and may be related to HCV-induced liver disease.

Computational identification of hepatitis C virus associated microRNA-mRNA regulatory modules in human livers

BACKGROUND

Hepatitis C virus (HCV) is a major cause of chronic liver disease by infecting over 170 million people worldwide. Recent studies have shown that microRNAs (miRNAs), a class of small non-coding regulatory RNAs, are involved in the regulation of HCV infection, but their functions have not been systematically studied. We propose an integrative strategy for identifying the miRNA-mRNA regulatory modules that are associated with HCV infection. This strategy combines paired expression profiles of miRNAs and mRNAs and computational target predictions. A miRNA-mRNA regulatory module consists of a set of miRNAs and their targets, in which the miRNAs are predicted to coordinately regulate the level of the target mRNA.

RESULTS

We simultaneously profiled the expression of cellular miRNAs and mRNAs across 30 HCV positive or negative human liver biopsy samples using microarray technology. We constructed a miRNA-mRNA regulatory network, and using a graph theoretical approach, identified 38 miRNA-mRNA regulatory modules in the network that were associated with HCV infection. We evaluated the direct miRNA regulation of the mRNA levels of targets in regulatory modules using previously published miRNA transfection data. We analyzed the functional roles of individual modules at the systems level by integrating a large-scale protein interaction network. We found that various biological processes, including some HCV infection related canonical pathways, were regulated at the miRNA level during HCV infection.

CONCLUSION

Our regulatory modules provide a framework for future experimental analyses. This report demonstrates the utility of our approach to obtain new insights into post-transcriptional gene regulation at the miRNA level in complex human diseases.

Caspase inhibitors for the treatment of hepatitis C

Decreasing hepatocyte injury and death is an attractive therapeutic target in chronic hepatitis C and other liver diseases. Apoptotic cell death is a critical mechanism responsible for liver injury in hepatitis C, and contributes to hepatic fibrogenesis. At the cellular level, apoptosis is executed by a family of cysteine proteases termed caspases. Caspase inhibitors have been developed to inhibit these proteases and attenuate cellular apoptosis in vivo. By reducing hepatocyte apoptosis these agents have the potential to serve as hepatoprotective agents, minimizing liver injury and fibrosis. Studies on a variety of animal models, and time-limited studies in human patients with hepatitis C suggest these are promising therapeutic agents. However, although these agents hold promise, their usefulness requires further studies, especially longer duration studies using hepatic fibrogenesis as the end point before they can be considered further for the treatment of patients infected with the hepatitis C virus.

Hypobetalipoproteinaemia secondary to chronic hepatitis C virus infection in a patient with familial hypercholesterolaemia

Familial hypercholesterolaemia (FH) is a common genetic disorder characterized by high plasma low-density lipoprotein (LDL)-cholesterol and premature coronary artery disease. Many factors, such as illness, high-dose statin therapy or a strict vegan diet can cause hypobetalipoproteinaemia (HBL). The more common secondary causes of HBL in the hospital setting include cachexia, intestinal malabsorption, malnutrition, severe liver disease and hyperthyroidism. We report a case of HBL in a 43-year-old man with previously demonstrated marked hypercholesterolaemia who attended a lipid disorders clinic for FH cascade screening. Surprisingly, a lipid profile taken at that time showed low plasma LDL-cholesterol and apolipoprotein B concentrations of 1.6 mmol/L and 0.61 g/L, respectively. He was not on lipid-lowering therapy. DNA sequencing showed that he was heterozygous for the LDLR gene mutation (C677R) present in other affected family members. Of interest, his serum transaminases were increased by approximately 3-fold and hepatitis serology and genotyping confirmed a diagnosis of hepatitis C virus (HCV) infection. In summary, we describe a case of HBL secondary to chronic HCV infection in a patient with FH, confirmed by mutational analysis.

Chronic viral hepatitis is a significant contributor to the immunosenescent phenotype of parenteral drug addiction

Intravenous drug addiction is known to be associated with an inordinate morbidity and mortality. As our previous report had identified an immune phenotype consistent with accelerated ageing, we wished to investigate how much of this change may have been related to chronic viral hepatitis. A total of 12 409 clinical pathology results from the period 1995-2007 were reviewed. To control for the differences in age, only patients less than 48 years of age were considered. A total of 636 substance use disorder (SUD) and 6103 non-SUD (N-SUD) patients were studied. They had comparable ages (mean +/- SD 31.32 +/- 6.90 versus 31.57 +/- 9.23, P-value not significant), but the SUD group had more males (74.37% versus 53.20%, P < 0.001). For most of the changes examined splitting the two SUD groups into hepatitis C positive (HCV+) and hepatitis C negative (HCV-) demonstrated that the majority of the described changes were most marked in the HCV+ group. The globulins were higher in the HCV+ group and the albumin was lower and fell more markedly with age than in N-SUD or HCV- (all P < 0.001). The globulin/albumin ratio was significantly higher in HCV+ than HCV- or N-SUD (both P < 0.0001) and rose more with age. These changes were paralleled by the ESR, elevations in the CRP and lymphocyte count. Transaminases were elevated in SUD and HCV+ groups compared with N-SUD (all P < 0.02). At multivariate analysis ESR, lymphocyte count, dual hepatitis B and C seropositivity, AST and HCVAb were significant predictors of the serum globulin level and accounted for 21% of the variance. These data extend our earlier report and show that much of the immunosenescent phenotype of SUD, encompassing the known immunosuppression and the observed immunostimulation, is statistically related to chronic viral hepatitis. Important theoretical and practical management (vaccination) implications ensue.

Hepatic stellate cell: a star cell in the liver

Hepatic stellate cells represent a highly versatile cytotype that plays a significant role in liver development and differentiation, regeneration, xenobiotic response, immunoregulation, control of hepatic blood flow and inflammatory reactions. Because of the wide panel of molecular intermediates they may produce and secrete, particularly after their sustained activation in a disease state, hepatic stellate cells are definitely involved in the pathogenesis of various liver pathologies, besides the well know key role in fibrosis and extracellular matrix remodelling. In particular, they can actively contribute to the progression of hepatitis and steatohepatitis of different aetiology, and of liver carcinogenesis.

Effects of silymarin on hepatitis C virus and haem oxygenase-1 gene expression in human hepatoma cells

BACKGROUND/AIMS

Hepatitis C virus (HCV) infection is a global medical problem. The current standard treatment of chronic hepatitis C (CHC), pegylated interferon plus ribavirin, is prolonged, expensive, has serious side effects and, at best, is only 50% effective. Silymarin (SI) is a natural antioxidant often used by patients with CHC, although its efficacy for decreasing HCV levels or ameliorating CHC remains uncertain. HCV infection is associated with increased hepatic oxidative stress, and one of the antioxidant enzymes that protect cells against this stress is haem oxygenase-1 (HO-1).

METHODS

We investigated effects of SI on HCV and HO-1 gene expression in Huh-7 cells, CNS3 and 9-13 cells (the latter two stably expressing HCV-proteins).

RESULTS

Silymarin significantly downregulated HCV core mRNA (by 20%-36%) and protein (by 30%-60%) in CNS3 cells. In contrast, SI did not decrease HCV NS5A mRNA or protein expression in 9-13 cells. HO-1 mRNA was upregulated (60%-400%) by SI in Huh-7, CNS3 and 9-13 cells, whereas BTB and CNC homology 1 and nuclear factor erythroid related factor 2 mRNA levels were not affected. The effect of SI to downregulate HCV core was not related to changes in the Janus-activated tyrosine kinases-signal transducer and activators of transcription signalling pathway.

CONCLUSIONS

Silymarin may be of benefit in CHC, although prospective, randomized, controlled trials are needed to be certain.

[Basic mechanisms of hepatocellular injury. Role of inflammatory lipid mediators]

The presence of a lesion in the cellular parenchyma is common to a large number of chronic liver diseases, such as viral hepatitides, alcoholic hepatitis, chronic cholestasis and steatohepatitis. Although the pathogenesis may vary according to the etiological agent, a series of mechanisms is common to all. Notable among these mechanisms are Kupffer cell activation and inflammatory cell recruitment, free oxygen radical formation and the development of oxidative stress, cytokine production, mainly TNFa and TGFb, and inflammatory mediator release due to arachidonic acid oxidation through the COX-2 and 5-LO pathways.

Genomic analysis reveals a potential role for cell cycle perturbation in HCV-mediated apoptosis of cultured hepatocytes

The mechanisms of liver injury associated with chronic HCV infection, as well as the individual roles of both viral and host factors, are not clearly defined. However, it is becoming increasingly clear that direct cytopathic effects, in addition to immune-mediated processes, play an important role in liver injury. Gene expression profiling during multiple time-points of acute HCV infection of cultured Huh-7.5 cells was performed to gain insight into the cellular mechanism of HCV-associated cytopathic effect. Maximal induction of cell-death-related genes and appearance of activated caspase-3 in HCV-infected cells coincided with peak viral replication, suggesting a link between viral load and apoptosis. Gene ontology analysis revealed that many of the cell-death genes function to induce apoptosis in response to cell cycle arrest. Labeling of dividing cells in culture followed by flow cytometry also demonstrated the presence of significantly fewer cells in S-phase in HCV-infected relative to mock cultures, suggesting HCV infection is associated with delayed cell cycle progression. Regulation of numerous genes involved in anti-oxidative stress response and TGF-beta1 signaling suggest these as possible causes of delayed cell cycle progression. Significantly, a subset of cell-death genes regulated during in vitro HCV infection was similarly regulated specifically in liver tissue from a cohort of HCV-infected liver transplant patients with rapidly progressive fibrosis. Collectively, these data suggest that HCV mediates direct cytopathic effects through deregulation of the cell cycle and that this process may contribute to liver disease progression. This in vitro system could be utilized to further define the cellular mechanism of this perturbation.

Is pegylated interferon superior to interferon, with ribavarin, in chronic hepatitis C genotypes 2/3?

Over the past decade, significant improvements have been made in the treatment of chronic hepatitis C (CHC), especially with the introduction of combined therapy using both interferon and ribavarin. The optimal dose and duration of treatment is still a matter of debate and, importantly, the efficacy of this combined treatment varies with the viral genotype responsible for infection. In general, patients infected with viral genotypes 2 or 3 more readily achieve a sustained viral response than those infected with viral genotype 1. The introduction of a pegylated version of interferon in the past decade has produced better clinical outcomes in patients infected with viral genotype 1. However, the published literature shows no improvement in clinical outcomes in patients infected with viral genotypes 2 or 3 when they are treated with pegylated interferon as opposed to non-pegylated interferon, both given in combination with ribavarin. This is significant because the cost of a 24-wk treatment with pegylated interferon in less-developed countries is between six and 30 times greater than that of treatment with interferon. Thus, clinicians need to carefully consider the cost-versus-benefit of using pegylated interferon to treat CHC, particularly when there is no evidence for clinically measurable benefits in patients with genotypes 2 and 3 infections.

Disease-specific mechanisms of fibrosis: hepatitis C virus and nonalcoholic steatohepatitis

Our mechanistic understanding of liver fibrosis has increased dramatically in recent years for all liver diseases and for hepatitis C and nonalcoholic steatohepatitis (NASH) in particular. Hepatitis C causes liver injury and fibrosis through direct cytopathic means, direct and indirect interactions with hepatic stellate cells, and activation of the immune system. Steatosis and insulin resistance, which are intrinsic deficits in NASH, are also of great importance in hepatitis C and may be induced by viral or host metabolic factors. For NASH, the key mediators of damage include oxidative stress, fat compartmentalization, visceral fat, apoptosis, and adipokine derangement. This article explores in depth the disease-specific mechanisms of fibrosis in hepatitis C and NASH, with a focus on recent developments.

Transplantation immunology: what the clinician needs to know for immunotherapy

The liver is unique among transplanted organs with respect to its interaction with the host immune system. There is evidence, both anecdotal and documented, that some liver recipients who cease taking immunosuppressive drugs maintain allograft function, suggesting robust tolerance is in place. Moreover, recipients of human liver allografts require less immunosuppression than do other organ recipients, and liver transplants confer protection on other organ grafts from the same donor. Hence, the liver shows features of immune privilege. Still, the liver can display destructive immunologic processes such as rejection in approximately one quarter of patients. The understanding of the cellular and molecular mechanisms operant in tolerance vs allograft rejection is important for developing new agents to improve long-term outcome, minimize infectious complications (including recurrence of hepatotropic viruses), and deliver immunosuppression without long-term toxicity. This review describes the unique aspects of the hepatic immune response, the pathways involved in T-cell activation and alloantigen recognition, effector cells and pathways mediating liver allograft rejection, the role of regulatory T cells, and targets of current and future immunosuppressive agents.

Advances in regulation mechanism of hepatocyte apoptosis in nonalcoholic fatty liver disease

The pathogenic mechanism of nonalcoholic fatty liver disease (NAFLD) still remains unclear. In recent years, many studies indicate that abnormal hepatocyte apoptosis exists in NAFLD, confirming the close relationship between NAFLD and hepatocyte apoptosis. The regulation of cell apoptosis includes two: positive or negative. In this paper, we review the research advances in the regulation of hepatocyte apoptosis during the pathogenesis of NAFLD.