Influence of ursodeoxycholate-enriched diet on liver tumor growth in HBV transgenic mice

A Pleiotropic Role of the Hepatitis B Virus Core Protein in Hepatocarcinogenesis

Chronic hepatitis B virus (HBV) infection is one of the most common factors associated with hepatocellular carcinoma (HCC), which is the sixth most prevalent cancer among all cancers worldwide. However, the pathogenesis of HBV-mediated hepatocarcinogenesis is unclear. Evidence currently available suggests that the HBV core protein (HBc) plays a potential role in the development of HCC, such as the HBV X protein. The core protein, which is the structural component of the viral nucleocapsid, contributes to almost every stage of the HBV life cycle and occupies diverse roles in HBV replication and pathogenesis. Recent studies have shown that HBc was able to disrupt various pathways involved in liver carcinogenesis: the signaling pathways implicated in migration and proliferation of hepatoma cells, apoptosis pathways, and cell metabolic pathways inducing the development of HCC; and the immune system, through the expression and production of proinflammatory cytokines. In addition, HBc can modulate normal functions of hepatocytes through disrupting human host gene expression by binding to promoter regions. This HBV protein also promotes HCC metastasis through epigenetic alterations, such as micro-RNA. This review focuses on the molecular pathogenesis of the HBc protein in HBV-induced HCC.

Multi-omic analysis in transgenic mice implicates omega-6/omega-3 fatty acid imbalance as a risk factor for chronic disease

An unbalanced increase in dietary omega-6 (n-6) polyunsaturated fatty acids (PUFA) and decrease in omega-3 (n-3) PUFA in the Western diet coincides with the global rise in chronic diseases. Whether n-6 and n-3 PUFA oppositely contribute to the development of chronic disease remains controversial. By using transgenic mice capable of synthesizing PUFA to eliminate confounding factors of diet, we show here that alteration of the tissue n-6/n-3 PUFA ratio leads to correlated changes in the gut microbiome and fecal and serum metabolites. Transgenic mice able to overproduce n-6 PUFA and achieve a high tissue n-6/n-3 PUFA ratio exhibit an increased risk for metabolic diseases and cancer, whereas mice able to convert n-6 to n-3 PUFA, and that have a lower n-6/n-3 ratio, show healthy phenotypes. Our study demonstrates that n-6 PUFA may be harmful in excess and suggests the importance of a low tissue n-6/n-3 ratio in reducing the risk for chronic diseases.

Enrichment of Ly6Chi monocytes by multiple GM-CSF injections with HBV vaccine contributes to viral clearance in a HBV mouse model

Adjuvants are considered a necessary component for HBV therapeutic vaccines but few are licensed in clinical practice due to concerns about safety or efficiency. In our recent study, we established that a combination protocol of 3-day pretreatments with GM-CSF before a vaccination (3 × GM-CSF+VACCINE) into the same injection site could break immune tolerance and cause over 90% reduction of HBsAg level in the HBsAg transgenic mouse model. Herein, we further investigated the therapeutic potential of the combination in AAV8–1.3HBV-infected mice. After 4 vaccinations, both serum HBeAg and HBsAg were cleared and there was a 95% reduction of HBV-positive hepatocytes, in addition to the presence of large number of infiltrating CD8⁺ T cells in the livers. Mechanistically, the HBV-specific T-cell responses were elicited via a 3 × GM-CSF+VACCINE-induced conversion of CCR2-dependent CD11b⁺ Ly6C^hi monocytes into CD11b⁺CD11c⁺ DCs. Experimental depletion of Ly6C^hi monocytes resulted in a defective HBV-specific immune response thereby abrogating HBV eradication. This vaccination strategy could lead to development of an effective therapeutic protocol against chronic HBV in infected patients.

Chenodeoxycholic acid increases the induction of CYP1A1 in HepG2 and H4IIE cells

Bile acids are considered to promote carcinogenesis. Cytochrome P450 1A1 (CYP1A1) plays a critical role in the biotransformation of drugs and procarcinogens. This study aimed to investigate the ability of bile acids to modulate CYP1A1 expression. Treatment of HepG2 cells with chenodeoxycholic acid (CDCA) and Sudan III (S.III) upregulated CYP1A1 transcriptional activity in HepG2 cells and CYP1A1 mRNA expression in H4IIE cells. Pretreatment of the HepG2 and H4IIE cells with CDCA upregulated the S.III-induced CYP1A transcriptional activity and mRNA expression. The CDCA-induced enhancement of CYP1A1 was not abolished by the p38 inhibitor SB203580. However, exposure of the cells to the mitogen-activated protein kinase kinase (MEK)1/2 inhibitor PD98059 suppressed the CDCA-induced enhancement of CYP1A1. These results show the ability of CDCA to upregulate CYP1A1 transcription and expression, which may explain the hepatocarcinogenesis-inducing effect of cholestasis. The CDCA-induced upregulation of CYP1A1 most probably proceeded through MEK1/2 activation, indicating that this may be a therapeutic target to prevent the cancer-promoting effects of excessive amounts of bile acids.

Bone marrow-derived stem cells and hepatocarcinogenesis in hepatitis B virus transgenic mice

BACKGROUND

Several studies have demonstrated that cancer can develop with the contribution of bone marrow-derived cancer stem cells. We evaluated the possible involvement of bone marrow-derived stem cells in hepatocarcinogenesis in a hepatitis B virus (HBV) transgenic mouse model.

METHODS

Bone marrow cells from wild type male mice were transplanted into sublethally irradiated, female, HBV transgenic mice with hepatocarcinoma nodules. Four months later, liver tissue was examined to localize neoplastic nodules/foci and characterize cells by evaluating the Y-chromosome and the hepatocyte lineage marker hepatocyte nuclear factor-1 (HNF1), as well as the HBsAg encoding gene (HBs-Eg) and HBsAg protein (HBs-Pr) (present only in cells of female origin).

RESULTS

Hepatocytes were HBs-Eg/HBs-Pr-positive in "normal" tissue, while resulted only HBs-Eg-positive in regenerative areas. Neoplastic foci/nodules were both HBs-Eg/HBs-Pr-negative. In the liver, 19 ± 5% of cells were Y-chromosome-positive and about one fifth were HNF1-positive. Y-chromosome and HBs-Eg colocalized in HNF1-positive cells. Y-chromosome-positive cells never localized in neoplastic foci/nodules (HBs-Pr/HBs-Eg-negative).

CONCLUSIONS

Bone marrow-derived stem cells participate in the hepatic regenerative process but not in neoplastic growth. Simultaneous detection of both Y-chromosome and HBs-Eg in the nucleus of an HNF1-positive cell (hepatocyte) demonstrates a phenomenon of cell fusion.

Hepatocyte metabolic signalling pathways and regulation of hepatitis B virus expression

Hepatitis B virus (HBV) is a small DNA virus responsible for significant morbidity and mortality worldwide. The liver, which is the main target organ for HBV infection, provides the virus with the machinery necessary for persistent infection and propagation, a process that might ultimately lead to severe liver pathologies such as chronic hepatitis, cirrhosis and liver cancer. HBV gene expression is regulated mainly at the transcriptional level by recruitment of a whole set of cellular transcription factors (TFs) and co-activators to support transcription. Over the years, many of these TFs were identified and interestingly enough most are associated with the body's nutritional state. These include the hepatocyte nuclear factors, forkhead Box O1, Farnesoid X receptor, cyclic-AMP response element-binding (CREB), CCAAT/enhancer-binding protein (C/EBP) and glucocorticoid receptor TFs and the transcription coactivator PPARγ coactivator-1α. Consequently, HBV gene expression is linked to hepatic metabolic processes such as glucose and fat production and utilization as well as bile acids' production and secretion. Furthermore, recent evidence indicates that HBV actively interferes with some of these hepatic metabolic processes by manipulating key TFs, such as CREB and C/EBP, to meet its requirements. The discovery of the mechanisms by which HBV is controlled by the hepatic metabolic milieu may broaden our understanding of the unique regulation of HBV expression and may also explain the mechanisms by which HBV induces liver pathologies. The emerging principle of the intimate link between HBV and liver metabolism can be further exploited for host-targeted therapeutic strategies.

Deciphering the nuclear bile acid receptor FXR paradigm

Originally called retinoid X receptor interacting protein 14 (RIP14), the farnesoid X receptor (FXR) was renamed after the ability of its rat form to bind supra-physiological concentrations of farnesol. In 1999 FXR was de-orphanized since primary bile acids were identified as natural ligands. Strongly expressed in the liver and intestine, FXR has been shown to be the master transcriptional regulator of several entero-hepatic metabolic pathways with relevance to the pathophysiology of conditions such as cholestasis, fatty liver disease, cholesterol gallstone disease, intestinal inflammation and tumors. Furthermore, given the importance of FXR in the gut-liver axis feedbacks regulating lipid and glucose homeostasis, FXR modulation appears to have great input in diseases such as metabolic syndrome and diabetes. Exciting results from several cellular and animal models have provided the impetus to develop synthetic FXR ligands as novel pharmacological agents. Fourteen years from its discovery, FXR has gone from bench to bedside; a novel nuclear receptor ligand is going into clinical use.

From chronic liver disorders to hepatocellular carcinoma: Molecular and genetic pathways

Hepatocarcinogenesis is a process attributed to progressive genomic changes that alter the hepatocellular phenotype producing cellular intermediates that evolve into hepatocellular carcinoma (HCC). During the preneoplastic phase, the liver is often the site of chronic hepatitis and/or cirrhosis, and these conditions induce liver regeneration with accelerated hepatocyte cycling in an organ that is otherwise proliferatively at rest. Hepatocyte regeneration is accelerated by upregulation of mitogenic pathways involving molecular and genetic mechanisms. Hepatic growth factors, inhibitors and triggers may also play a role. This process leads to the production of monoclonal populations of aberrant and dysplastic hepatocytes that have telomerase re-expression, microsatellite instability, and occasionally structural aberrations in genes and chromosomes. Development of dysplastic hepatocytes in foci and nodules and the emergence of HCC are associated with the accumulation of irreversible structural alterations in genes and chromosomes even if the genomic basis of the malignant phenotype is largely heterogeneous. Therefore, a malignant hepatocyte phenotype may be produced by changes in genes acting through different regulatory pathways, thus producing several molecular variants of HCC. On these bases, a key point for future research will be to determine whether the deletions are specific, due to particular loci in the minimally deleted regions of affected chromosome arms, or whether they are non-specific with loss of large portions of chromosomes or entire chromosome arms leading to passive deletion of loci. The final aim is the possibility of identifying a step where carcinogenetic processes could be terminated.

Possible involvement of androgen receptor alterations in hepatocarcinogenesis

BACKGROUND

Androgen receptors (ARs) act as transcription factors. An increased AR activity could be due either to mutations or to an increased expression of the receptor. AR mutations involving the hormone binding domain could increase AR function and promote carcinogenesis, as suggested for prostate cancer.

AIMS

Herein, we evaluated qualitative (point mutations involving the hormone binding domain) and quantitative AR alterations and their possible correlation with cell proliferation and tumour grading.

MATERIALS

Carcinomatous and non-cancerous surrounding liver tissue was collected from 14 Caucasian patients with hepatocarcinoma. They were all affected by cirrhosis with different aetiologies.

METHODS

AR missense mutations, AR mRNA and protein levels, AR distribution in the liver, liver cell proliferation, and tumour staging were evaluated by DNA sequencing, quantitative real-time PCR, Western blot analysis, immunofluorescence, PCNA immunostaining, and conventional histological techniques, respectively.

RESULTS

AR gene regions encoding the hormone binding domain did not contain any missense mutation. AR mRNA and protein levels were increased in hepatocarcinoma compared to non-cancerous surrounding tissue. Cell proliferation was significantly increased in the tumour compared to non-cancerous surrounding tissue.

CONCLUSIONS

Mutations of the AR regions studied were not involved in hepatocarcinogenesis. Elevated AR levels in transformed cells could have a tumour promoting effect by stimulating cell growth.

Effect of gonadectomy on HCC development in HBV transgenic mice

BACKGROUND AND AIMS

Epidemiological data demonstrate that HCC is prevalent in men compared to women. Herein, we examined the effect of gonadectomy in a murine model that spontaneously develops HCC.

ANIMALS AND METHODS

Thirty-two male and 26 female HBV transgenic mice [Tg (Alb-1 HBV) Bri 44] underwent surgical castration or sham operation. At the 18th month, serum samples were collected and all mice were sacrificed. Liver weight and volume were evaluated, each liver was cut into 1.5-mm-thick consecutive slices and nodules were examined on freshly isolated tissue. Consecutive histological sections obtained from each liver slice were evaluated to confirm the diagnosis of HCC.

RESULTS

Sham-operated females showed a significantly lower neoplastic growth compared to sham-operated males. This difference disappeared when females underwent gonadectomy. In males, neoplastic growth was not influenced by gonadectomy. Testosterone and estradiol levels were profoundly modified by gonadectomy in both males and females. The testosterone/estradiol ratio in gonadectomized females increased 4.5-fold compared to that in sham-operated females, becoming more similar to the ratio observed in castrated and sham-operated male mice.

CONCLUSIONS

HCC growth in our experimental model was not simply influenced by the levels of testosterone or estradiol, taken singularly, but depended on their ratio.

FXR: a metabolic regulator and cell protector

Farnesoid X receptor (FXR) is a member of the nuclear receptor superfamily of ligand-activated transcription factors. As a metabolic regulator, FXR plays key roles in bile acid, cholesterol, lipid, and glucose metabolism. Therefore, FXR is a potential drug target for a number of metabolic disorders, especially those related to the metabolic syndrome. More recently, our group and others have extended the functions of FXR to more than metabolic regulation, which include anti-bacterial growth in intestine, liver regeneration, and hepatocarcinogenesis. These new findings suggest that FXR has much broader roles than previously thought, and also highlight FXR as a drug target for multiple diseases. This review summarizes the basic information of FXR but focuses on its new functions.

Hepatitis B virus core protein inhibits TRAIL-induced apoptosis of hepatocytes by blocking DR5 expression

Hepatitis B virus (HBV) causes chronic hepatitis in hundreds of millions of people worldwide, which can eventually lead to hepatocellular carcinoma (HCC). The molecular mechanisms underlying HBV persistence are not well understood. TRAIL, the TNF-related apoptosis-inducing ligand, has recently been implicated in hepatocyte death during HBV infection. We report here that the HBV core protein (HBc) is a potent inhibitor of TRAIL-induced apoptosis. Overexpressing HBc significantly decreased TRAIL-induced apoptosis of human hepatoma cells, whereas knocking-down HBc expression in hepatoma cells transfected with HBV genome enhanced it. When present in the same cell, HBc blocked the pro-apoptotic effect of the HBV X protein (HBx). The resistance of HBc-expressing cells to TRAIL-induced apoptosis was associated with a significant reduction in death receptor 5 (DR5) expression. Upon transfection, HBc significantly repressed the promoter activity of the human DR5 gene. Importantly, HBc gene transfer inhibited hepatocyte death in a mouse model of HBV-induced hepatitis; and in patients with chronic hepatitis, DR5 expression in the liver was significantly reduced. These results indicate that HBc may prevent hepatocytes from TRAIL-induced apoptosis by blocking DR5 expression, which in turn contributes to the development of chronic hepatitis and HCC. They also call into question the potential side effects of HBc-based vaccines.

ER-beta expression in large bowel adenomas: implications in colon carcinogenesis

BACKGROUND

A pivotal role of oestrogen receptor-beta has been suggested in colon carcinogenesis in humans. However, few data are available on oestrogen receptor-beta in colorectal pre-cancerous lesions.

AIM

In the present study, we evaluated oestrogen receptor-beta expression and its possible correlation with proliferative activity and apoptosis in colorectal adenomas and normal colon tissue.

PATIENTS/METHODS

Adenomatous tissue from 25 patients with colonic polyps, and normal tissue from 25 controls were used. Oestrogen receptor-beta expression, colonocyte proliferation (expressed as PCNA positivity) and apoptosis were evaluated.

RESULTS

In adenomatous tissue, a significant reduction of oestrogen receptor-beta was observed compared to normal mucosa (10.1+/-5.5% vs. 44.2+/-13.7; p<0.03), while the expression of oestrogen receptor-alpha remained unvaried. Cell proliferative activity significantly increased in adenomatous tissue compared to normal mucosa (59.3+/-7.1 vs. 18.5+/-8.8; p<0.0001), doubling the PCNA/apoptosis ratio. An inverse correlation was found between oestrogen receptor-beta and PCNA expression in adenomas (r=-0.81), a datum confirmed by confocal microscopy evaluation.

CONCLUSIONS

Our data demonstrate, for the first time, a significant reduction of oestrogen receptor-beta expression already in the pre-cancerous phase of colon carcinogenesis. This suggests a role of selective oestrogen receptor-beta agonists in the prevention of colorectal cancer.

Spontaneous development of liver tumors in the absence of the bile acid receptor farnesoid X receptor

Farnesoid X receptor (FXR, NR1H4) is a member of the nuclear hormone receptor superfamily, which plays an essential role in regulating bile acid, lipid, and glucose homeostasis. Both male and female FXR(-/-) mice spontaneously developed liver tumors; however, no other tumors were developed after 15 months of age. In contrast, no liver tumors were observed in wild-type mice of the same age. Histologic analyses confirm that tumors were hepatocellular adenoma and carcinoma. Although there was no obvious tumor at ages 9 to 12 months, FXR(-/-) livers displayed prominent liver injury and inflammation. Strong labeling of apoptotic hepatocytes and liver damage-induced compensatory regeneration were observed. Deregulation of genes involved in bile acid homeostasis in FXR(-/-) mice was consistent with abnormal levels of bile acids presented in serum and liver. Genes involved in inflammation and cell cycle were up-regulated in aging FXR(-/-) mice but not in wild-type controls. Increasing the bile acid levels by feeding mice with a 0.2% cholic acid diet strongly promoted N-nitrosodiethylamine-initiated liver tumorigenesis, whereas lowering bile acid pool in FXR(-/-) mice by a 2% cholestyramine feeding significantly reduced the malignant lesions. Our results suggest an intriguing link between metabolic regulation and hepatocarcinogenesis.

Ursodeoxycholate further increases bile-duct cell proliferative response induced by partial bile-duct ligation in rats

BACKGROUND

Bile salts (BSs) stimulate cholangiocyte proliferation in vitro and in vivo in normal rats. In this study, we evaluated the effects of BS-enriched diets on cholangiocyte proliferative activity already triggered by partial bile-duct ligation (pBDL), a surgical model that induces mild cholestatic conditions, focusing our attention on ursodeoxycholate (UDC).

METHODS

Animals (n=45) were fed either a standard diet, or a 0.2% deoxycholate- or 0.2% UDC-enriched diet for 4 weeks. Then, in each group, ten animals underwent pBDL and five underwent sham operation. Serum and biliary BS levels, serum cholestasis and cytolysis indexes, as well as liver conventional histology, apoptosis and proliferative activity were evaluated 48 h after the operation.

RESULTS

Animals that underwent pBDL showed sustained proliferative response compared with sham-operated rats. BS-enriched diets did not influence cholangiocyte proliferation in sham-operated rats. However, significantly increased proliferation was observed in pBDL rats fed a UDC-enriched diet. The evaluation of humoral and histological parameters excluded the possibility that the increased proliferation induced by UDC-enriched diet could be related to concomitant liver cell damage.

CONCLUSION

A UDC-enriched diet is able to amplify the magnitude of the cholangiocyte hyperplastic process, which occurs by a stimulatory mechanism after partial bile-duct ligation.

Cholestatic syndromes

PURPOSE OF REVIEW

This review highlights recent developments in the molecular pathogenesis of cholestasis as well new aspects of pathogenesis and management of clinical cholestatic disorders.

RECENT FINDINGS

Highlights include the role of nuclear receptors including FXR ligands as potential therapeutic agents, new genetic defects for pediatric cholestasis and sclerosing cholangitis, and novel infections and environmental agents as etiologies for primary biliary cirrhosis. Important clinical studies have been published in the area of pediatric cholestatic syndromes, intrahepatic cholestasis of pregnancy, primary biliary cirrhosis, primary and secondary sclerosing cholangitis, cholestasis of sepsis, viral cholestatic syndromes, and drug-induced cholestasis.

SUMMARY

These advances continue to improve understanding of the pathophysiology, diagnosis, and management of cholestatic liver disease.

Inhibitory effect of oxymatrine on expression of hepatitis B virus in HBV transgenic mice

AIM: To study the inhibitory effect of oxymatrine on HBsAg, HBeAg, and HBcAg expression in the liver tissue of HBV transgenic mice, and to further expound the mechanisms of oxymatrine anti-HBV.

METHODS: HBV transgenic mice models were established by microinjecting methods, and detected by HBV DNA integration and replication. Replicating HBV transgenic mice were divided into three groups: injected with normal saline (n = 9), 50 mg/kg (n = 8) and 100mg/kg (n = 9) oxymatrine intraperitonealy once a day for 30 d, respectively. After treatment, detection of HBsAg and HBeAg by ELISA, HBsAg and HBcAg by immunohistochemistry in the liver tissues was conducted.

RESULTS: Compared with group normal saline, HBsAg content in 50 mg/kg and 100 mg/kg oxymatrine decreased, but there was no statistic significance (F = 1.29, P>0.05). Compared with normal saline group, HBeAg content in 50 mg/kg and 100 mg/kg oxymatrine groups obviously decreased(F = 9.09, P < 0.01), but there was no obvious significance between 50 mg/kg and 100 mg/kg oxymatrine groups (F = 1.58, P> 0.05). The number of HbsAg-positive cells in the normal saline group, 50 mg/kg and 100 mg/kg oxymatrine had no changes in the liver tissues (x² = 1.61, P> 0.05). The number of HBcAg-positive cells in the liver tissues was significantly lower in the group of 100 mg/kg oxymatrine than that in the group of normal saline (x²= 4.73, P < 0.05), but the number between normal saline group and 50 mg/kg oxymatrine group, and between the groups of 50 mg/kg and 100 mg/kg oxymatrine had no obvious significance.

CONCLUSION: There is an inhibitory effect of oxymatrine on expression of hepatitis B virus in HBV transgenic mice.

Systematic review: ursodeoxycholic acid--adverse effects and drug interactions

BACKGROUND

Ursodeoxycholic acid is increasingly being used for the treatment of chronic cholestatic liver diseases. It appears to be generally well tolerated, but a systematic review on drug safety is lacking.

AIM

As experimental data suggest a role of bile acids in the regulation of hepatic drug metabolism at both the transcriptional and post-transcriptional level, the literature was screened for adverse drug reactions and drug interactions related to ursodeoxycholic acid.

METHODS

A systematic review of the literature was performed using a refined search strategy to evaluate the adverse effects of ursodeoxycholic acid and its interactions with other drugs.

RESULTS

Ursodeoxycholic acid caused diarrhoea in a small proportion of patients. Rare skin reactions were due to drug adjuvants rather than the active substance. Decompensation of liver cirrhosis was reported after the administration of ursodeoxycholic acid in single cases of end-stage primary biliary cirrhosis. Recurrent right upper quadrant abdominal pain was incidentally observed. The absorption of ursodeoxycholic acid was impaired by colestyramine, colestimide, colestipol, aluminium hydroxide and smectite. Metabolic drug interactions were reported for the cytochrome P4503A substrates, ciclosporin, nitrendipine and dapsone.

CONCLUSIONS

Ursodeoxycholic acid is generally well tolerated. Drug absorption interactions with anion exchange resins deserve consideration. Metabolic interactions with compounds metabolized by cytochrome P4503A are to be expected.