Up-regulation of proproliferative genes and the ligand/receptor pair placental growth factor and vascular endothelial growth factor receptor 1 in hepatitis C cirrhosis

CpG DNA-triggered upregulation of TLR9 expression affects apoptosis and immune responses in human plasmacytoid dendritic cells isolated from chronic hepatitis B patients

Plasmacytoid dendritic cells (pDCs) were treated with cytosine-phosphate-guanine (CpG) DNA, and cell apoptosis, signals and immune responses were measured to investigate the effects and mechanism of CpG DNA in pDCs from chronic hepatitis B patients. CpG DNA-stimulated pDCs secreted more IFN-α than the control pDCs. CpG DNA activated Toll-like receptor 9 (TLR9), thereby resulting in the upregulated expression of myeloid differentiation primary response gene 88 (MyD88), interferon regulatory factor 7 (IRF7) and nuclear factor kappa B (NF-κB). Furthermore, CpG DNA down-regulated apoptosis and promoted the expression of IFN-α, interleukin-12 (IL-12), IL-21, IL-26 and tumour necrosis factor-α (TNF-α) in pDCs. Following treatment with NF-κB inhibitor, pyrollidine dithiocarbamate (PDTC), the influence of CpG DNA on pDCs was inhibited. Our results suggest that CpG DNA may directly interfere with the function of pDCs through TLR9-mediated upregulation of MyD88, IRF7 and NF-κB expression, which can partially explain the activation of pDCs in chronic hepatitis B patients.

Placental growth factor levels neither reflect severity of portal hypertension nor portal-hypertensive gastropathy in patients with advanced chronic liver disease

BACKGROUND & AIMS

Experimental data indicates that placental growth factor (PLGF) is involved in the pathophysiology of portal hypertension (PH) due to advanced chronic liver disease (ACLD). We investigated serum levels of PLGF and its "scavenger", the receptor soluble fms-like tyrosine kinase-1 (sFLT1, or sVEGFR1), in ACLD patients with different severity of PH and portal-hypertensive gastropathy (PHG).

METHODS

PLGF and sVEGFR1 were measured in ACLD patients with hepatic venous pressure gradient (HVPG) ≥6 mmHg (n = 241) and endoscopic evaluation of PHG (n = 216). Patients with pre-/posthepatic PH, TIPS, liver transplantation and hepatocellular carcinoma were excluded.

RESULTS

Thirty-two (13%) patients had HVPG 6-9 mmHg, 128 (53%) 10-19 mmHg and 81 (34%) ≥20 mmHg; 141 (59%) had decompensated ACLD (dACLD). PLGF (median 17.2 vs. 20.8 vs. 22.4 pg/mL; p = 0.002), sVEGFR1 (median 96.0 vs. 104.8 vs. 119.3 pg/mL; p < 0.001) levels increased across HVPG strata, while PLGF/sVEGFR1 ratios remained similar (0.19 vs. 0.20 vs. 0.18 pg/mL; p = 0.140). The correlation between PLGF and HVPG was weak (Rho = 0.190,95%CI 0.06-0.31; p = 0.003), and the PLGF/sVEGFR1 ratio did not correlate with HVPG (p = 0.331). The area-under-the-receiver operating characteristics (AUROC) for PLGF to detect clinically significant PH (CSPH;i.e. HVPG ≥ 10 mmHg) yielded only 0.688 (0.60-0.78; p < 0.001). When compared to ACLD patients without PHG, PLGF levels (20 without vs. 21.4 with mild vs. 17.1 pg/mL with severe PHG, respectively; p = 0.005) and PLGF/sVEGFR1 ratios (0.20 vs. 0.19 vs. 0.17; p = 0.076) did not increase with mild and severe PHG.

CONCLUSION

While PLGF levels tended to increase with severity of PH, the PLGF/sVEGFR1 ratio remained stable across HVPG strata. Neither PLGF nor the PLGF/sVEGFR1 ratio had diagnostic value for prediction of CSPH. The severity of PHG was also not associated with stepwise increases in PLGF levels or PLGF/sVEGFR1 ratio.

The Worst Things in Life are Free: The Role of Free Heme in Sickle Cell Disease

Hemolysis is a pathological feature of several diseases of diverse etiology such as hereditary anemias, malaria, and sepsis. A major complication of hemolysis involves the release of large quantities of hemoglobin into the blood circulation and the subsequent generation of harmful metabolites like labile heme. Protective mechanisms like haptoglobin-hemoglobin and hemopexin-heme binding, and heme oxygenase-1 enzymatic degradation of heme limit the toxicity of the hemolysis-related molecules. The capacity of these protective systems is exceeded in hemolytic diseases, resulting in high residual levels of hemolysis products in the circulation, which pose a great oxidative and proinflammatory risk. Sickle cell disease (SCD) features a prominent hemolytic anemia which impacts the phenotypic variability and disease severity. Not only is circulating heme a potent oxidative molecule, but it can act as an erythrocytic danger-associated molecular pattern (eDAMP) molecule which contributes to a proinflammatory state, promoting sickle complications such as vaso-occlusion and acute lung injury. Exposure to extracellular heme in SCD can also augment the expression of placental growth factor (PlGF) and interleukin-6 (IL-6), with important consequences to enthothelin-1 (ET-1) secretion and pulmonary hypertension, and potentially the development of renal and cardiac dysfunction. This review focuses on heme-induced mechanisms that are implicated in disease pathways, mainly in SCD. A special emphasis is given to heme-induced PlGF and IL-6 related mechanisms and their role in SCD disease progression.

Whole-Exome Sequencing to Identify Novel Biological Pathways Associated With Infertility After Pelvic Inflammatory Disease

BACKGROUND

Ideal management of sexually transmitted infections (STI) may require risk markers for pathology or vaccine development. Previously, we identified common genetic variants associated with chlamydial pelvic inflammatory disease (PID) and reduced fecundity. As this explains only a proportion of the long-term morbidity risk, we used whole-exome sequencing to identify biological pathways that may be associated with STI-related infertility.

METHODS

We obtained stored DNA from 43 non-Hispanic black women with PID from the PID Evaluation and Clinical Health Study. Infertility was assessed at a mean of 84 months. Principal component analysis revealed no population stratification. Potential covariates did not significantly differ between groups. Sequencing kernel association test was used to examine associations between aggregates of variants on a single gene and infertility. The results from the sequencing kernel association test were used to choose "focus genes" (P < 0.01; n = 150) for subsequent Ingenuity Pathway Analysis to identify "gene sets" that are enriched in biologically relevant pathways.

RESULTS

Pathway analysis revealed that focus genes were enriched in canonical pathways including, IL-1 signaling, P2Y purinergic receptor signaling, and bone morphogenic protein signaling.

CONCLUSIONS

Focus genes were enriched in pathways that impact innate and adaptive immunity, protein kinase A activity, cellular growth, and DNA repair. These may alter host resistance or immunopathology after infection. Targeted sequencing of biological pathways identified in this study may provide insight into STI-related infertility.

Bone morphogenetic proteins as regulators of iron metabolism

Bone morphogenetic proteins (BMPs) are members of the transforming growth factor-beta (TGF-β) superfamily of signaling molecules. In addition to protean roles in embryonic development, germ-line specification, and cellular differentiation, a central role in iron homeostasis has recently been demonstrated for certain BMPs. Specifically, BMP6 serves to relate hepatic iron stores to the hepatocellular expression of the iron-regulatory hormone hepcidin. This regulation occurs via cellular SMAD-signaling molecules and is strongly modulated by the BMP coreceptor hemojuvelin (HJV). Mutations in certain genes influencing signaling to hepcidin via the BMP/SMAD pathway are associated with human disorders of iron metabolism, such as hereditary hemochromatosis and iron-refractory iron-deficiency anemia. Evidence suggests that signals in addition to iron stores influence hepcidin expression via the BMP/SMAD pathway. This review summarizes the details of BMP/SMAD signaling, with a particular focus on its role in iron homeostasis and iron-related diseases.

Paracrine signals from liver sinusoidal endothelium regulate hepatitis C virus replication

Hepatitis C virus (HCV) is a major cause of global morbidity, causing chronic liver injury that can progress to cirrhosis and hepatocellular carcinoma. The liver is a large and complex organ containing multiple cell types, including hepatocytes, sinusoidal endothelial cells (LSEC), Kupffer cells, and biliary epithelial cells. Hepatocytes are the major reservoir supporting HCV replication; however, the role of nonparenchymal cells in the viral lifecycle remains largely unexplored. LSEC secrete factors that promote HCV infection and transcript analysis identified bone morphogenetic protein 4 (BMP4) as a candidate endothelial-expressed proviral molecule. Recombinant BMP4 increased HCV replication and neutralization of BMP4 abrogated the proviral activity of LSEC-conditioned media. Importantly, BMP4 expression was negatively regulated by vascular endothelial growth factor A (VEGF-A) by way of a VEGF receptor-2 (VEGFR-2) primed activation of p38 MAPK. Consistent with our in vitro observations, we demonstrate that in normal liver VEGFR-2 is activated and BMP4 expression is suppressed. In contrast, in chronic liver disease including HCV infection where there is marked endothelial cell proliferation, we observed reduced endothelial cell VEGFR-2 activation and a concomitant increase in BMP4 expression.

CONCLUSION

These studies identify a role for LSEC and BMP4 in HCV infection and highlight BMP4 as a new therapeutic target for treating individuals with liver disease.

Hepatitis C virus induced miR200c down modulates FAP-1, a negative regulator of Src signaling and promotes hepatic fibrosis

Hepatitis C virus (HCV) induced liver disease is the leading indication for liver transplantation (LTx). Reinfection and accelerated development of fibrosis is a universal phenomenon following LTx. The molecular events that lead to fibrosis following HCV infection still remains poorly defined. In this study, we determined microRNA (miRNA) and mRNA expression profiles in livers from chronic HCV patients and normals using microarrays. Using Genego software and pathway finder we performed an interactive analysis to identify target genes that are modulated by miRNAs. 22 miRNAs were up regulated (>2 fold) and 35 miRNAs were down regulated (>2fold) compared to controls. Liver from HCV patients demonstrated increased expression of 306 genes (>3 fold) and reduced expression of 133 genes (>3 fold). Combinatorial analysis of the networks modulated by the miRNAs identified regulation of the phospholipase C pathway (miR200c, miR20b, and miR31through cellular proto-oncogene tyrosine-protein kinase Src (cSrc)), response to growth factors and hormones (miR141, miR107 and miR200c through peroxisome proliferator-activated receptor alpha and extracellular-signal-regulated kinases, and regulation of cellular proliferation (miR20b, miR10b, and miR141 through cyclin-dependent kinase inhibitor 1 or CDK-interacting protein 1 p21). Real time PCR (RT-PCR) validation of the miRNA in HCV infected livers demonstrated a 3.3 ±0.9 fold increase in miR200c. In vitro transfection of fibroblasts with miR200c resulted in a 2.2 fold reduction in expression of tyrosine-protein phosphatase non-receptor type 13 or FAS associated phosphatase 1 (FAP-1) and 2.3 fold increase in expression of cSrc. miR200c transfection resulted in significant increases in expression of collagen and fibroblast growth factor (2.8 and 3.4 fold, p<0.05). Therefore, we propose that HCV induced increased expression of miR200c can down modulate the expression of FAP1, a critical regulator of Src and MAP kinase pathway that play an important role in the production of fibrogenic growth factors and development of fibrosis.

Hepatitis C virus-related hepatocellular carcinoma: An insight into molecular mechanisms and therapeutic strategies

Hepatitis C virus (HCV) infects more than 170 million people worldwide, and thereby becomes a series global health challenge. Chronic infection with HCV is considered one of the major causes of end-stage liver disease including cirrhosis and hepatocellular carcinoma. Although the multiple functions of the HCV proteins and their impacts on the modulation of the intracellular signaling transduction processes, the drive of carcinogenesis during the infection with HCV, is thought to result from the interactions of viral proteins with host cell proteins. Thus, the induction of mutator phenotype, in liver, by the expression of HCV proteins provides a key mechanism for the development of HCV-associated hepatocellular carcinoma (HCC). HCC is considered one of the most common malignancies worldwide with increasing incidence during the past decades. In many countries, the trend of HCC is attributed to several liver diseases including HCV infection. However, the development of HCC is very complicated and results mainly from the imbalance between tumor suppressor genes and oncogenes, as well as from the alteration of cellular factors leading to a genomic instability. Besides the poor prognosis of HCC patients, this type of tumor is quite resistance to the available therapies. Thus, understanding the molecular mechanisms, which are implicated in the development of HCC during the course of HCV infection, may help to design a general therapeutic protocol for the treatment and/or the prevention of this malignancy. This review summarizes the current knowledge of the molecular mechanisms, which are involved in the development of HCV-associated HCC and the possible therapeutic strategies.

Analysis of human liver disease using a cluster of differentiation (CD) antibody microarray

BACKGROUND

A CD antibody microarray has been previously developed allowing semi-quantitative identification of greater than 80 CD antigens on circulating leucocytes from peripheral blood samples. This assay, which uses a live cell-capture technique, enables an extensive leucocyte immunophenotype determination in a single analysis and to date this has been used successfully to characterise diseases including human leukaemias and HIV infection.

AIMS

To determine CD antigen expression profiles for patients with various liver diseases and to look for preserved disease-specific signatures.

METHODS

Three liver disease groups including hepatitis C (HCV) (n = 35), non-alcoholic steatohepatitis (NASH) (n = 21) and alcohol-related liver disease (n = 14) were compared with a normal group (n = 23). Hierarchal Clustering (HCL) and Principal Component Analysis (PCA) of the data revealed distinct binding patterns for patients with and without cirrhosis.

RESULTS

Patients with cirrhosis and portal hypertension compared with those without cirrhosis had significantly reduced expression of several markers of T-cell function including CD45, CD8, CD28 and TCR α/β. Disease prediction algorithms based on the expression data were able to discriminate cirrhotics from non-cirrhotics with 71% overall success, which improved to 77% when only patients with HCV were considered.

CONCLUSIONS

These results demonstrate disease-specific consensus patterns of expression of CD antigens for patients with chronic liver disease, suggesting that the CD antibody array is a promising tool in the analysis of human liver disease, and with further refinement may have future research and clinical utility.

PlGF: a multitasking cytokine with disease-restricted activity

Placental growth factor (PlGF) is a member of the vascular endothelial growth factor (VEGF) family that also comprises VEGF-A (VEGF), VEGF-B, VEGF-C, and VEGF-D. Unlike VEGF, PlGF is dispensable for development and health but has diverse nonredundant roles in tissue ischemia, malignancy, inflammation, and multiple other diseases. Genetic and pharmacological gain-of-function and loss-of-function studies have identified molecular mechanisms of this multitasking cytokine and characterized the therapeutic potential of delivering or blocking PlGF for various disorders.

Regulation of placenta growth factor by microRNA-125b in hepatocellular cancer

BACKGROUND & AIMS

microRNAs (miRNAs) are a class of small noncoding RNAs that can regulate gene expression by translation repression or mRNA degradation. Our aim was to evaluate the role of aberrantly expressed miRNAs in hepatocellular cancer (HCC).

METHODS

miRNA expression in HCC tissues and cells was evaluated by qPCR array and Taqman miRNA assay. Cell proliferation, motility, invasion, and the angiogenesis index were quantitated using commercial assays. DNA methylation status, matrix metalloproteinases (MMPs) mRNA expression was quantitated by real-time PCR analysis.

RESULTS

miRNA profiling identified a decrease in miR-125b expression in HCC tumor tissues and cell lines. The expression of miR-125b was significantly increased by the methylation inhibitor 5-aza-2'-deoxycytidine in HCC cells but not in normal controls, suggesting that the expression of miR-125b could be epigenetically modulated. Methylation-specific PCR revealed hypermethylation status of miR-125b in HCC cells compared to non-malignant controls. Cell proliferation, anchorage-independent growth, cell migration, invasion, and angiogenesis were significantly decreased by the introduction of miR-125b precursor in HCC cell lines. Placenta growth factor was identified as a target of miR-125b by bioinformatics analysis and experimentally verified using luciferase reporter constructs. Overexpression of miR-125b in HCC cells decreased PIGF expression, and altered the angiogenesis index. Furthermore, modulation of miR-125b also distorted expression of MMP-2 and -9, the mediators of enzymatic degradation of the extracellular matrix.

CONCLUSIONS

Our studies showing epigenetic silencing of miR-125b contributes to an invasive phenotype provide novel mechanistic insights and identify a potential target mechanism that could be manipulated for therapeutic benefit in HCC.

Discoidin domain receptor 1: isoform expression and potential functions in cirrhotic human liver

Discoidin domain receptor 1 (DDR1) is a receptor tyrosine kinase that binds and is activated by collagens. Transcriptional profiling of cirrhosis in human liver using a DNA array and quantitative PCR detected elevated mRNA expression of DDR1 compared with that in nondiseased liver. The present study characterized DDR1 expression in cirrhotic and nondiseased human liver and examined the cellular effects of DDR1 expression. mRNA expression of all five isoforms of DDR1 was detected in human liver, whereas DDR1a demonstrated differential expression in liver with hepatitis C virus and primary biliary cirrhosis compared with nondiseased liver. In addition, immunoblot analysis detected shed fragments of DDR1 more readily in cirrhotic liver than in nondiseased liver. Inasmuch as DDR1 is subject to protease-mediated cleavage after prolonged interaction with collagen, this differential expression may indicate more intense activation of DDR1 protein in cirrhotic compared with nondiseased liver. In situ hybridization and immunofluorescence localized intense DDR1 mRNA and protein expression to epithelial cells including hepatocytes at the portal-parenchymal interface and the luminal aspect of the biliary epithelium. Overexpression of DDR1a altered hepatocyte behavior including increased adhesion and less migration on extracelular matrix substrates. DDR1a regulated extracellular expression of matrix metalloproteinases 1 and 2. These data elucidate DDR1 function pertinent to cirrhosis and indicate the importance of epithelial cell-collagen interactions in chronic liver injury.

Inhibition of placental growth factor activity reduces the severity of fibrosis, inflammation, and portal hypertension in cirrhotic mice

Placental growth factor (PlGF) is associated selectively with pathological angiogenesis, and PlGF blockade does not affect the healthy vasculature. Anti-PlGF is therefore currently being clinically evaluated for the treatment of cancer patients. In cirrhosis, hepatic fibrogenesis is accompanied by extensive angiogenesis. In this paper, we evaluated the pathophysiological role of PlGF and the therapeutic potential of anti-PlGF in liver cirrhosis. PlGF was significantly up-regulated in the CCl(4) -induced rodent model of liver cirrhosis as well as in cirrhotic patients. Compared with wild-type animals, cirrhotic PlGF(-/-) mice showed a significant reduction in angiogenesis, arteriogenesis, inflammation, fibrosis, and portal hypertension. Importantly, pharmacological inhibition with anti-PlGF antibodies yielded similar results as genetic loss of PlGF. Notably, PlGF treatment of activated hepatic stellate cells induced sustained extracellular signal-regulated kinase 1/2 phosphorylation, as well as chemotaxis and proliferation, indicating a previously unrecognized profibrogenic role of PlGF.

CONCLUSION

PlGF is a disease-candidate gene in liver cirrhosis, and inhibition of PlGF offers a therapeutic alternative with an attractive safety profile.

Recent insights into the role of Toll-like receptors in viral infection

Toll-like receptors (TLRs) have a central role in innate immunity as they detect conserved pathogen-associated molecular patterns (PAMPs) on a range of microbes, including viruses, leading to innate immune activation and orchestration of the adaptive immune response. To date, a large number of viruses have been shown to trigger innate immunity via TLRs, suggesting that these receptors are likely to be important in the outcome to viral infection. This suggestion is supported by the observation that many viruses have evolved mechanisms not only to evade the innate immune system, but also to subvert it for the benefit of the virus. In this review we will discuss earlier evidence, mainly from knock-out mice studies, implicating TLRs in the innate immune response to viruses, in light of more recent clinical data demonstrating that TLRs are important for anti-viral immunity in humans.

Prevalence and challenges of liver diseases in patients with chronic hepatitis C virus infection

Hepatitis C virus (HCV) infections pose a growing challenge to health care systems. Although chronic HCV infection begins as an asymptomatic condition with few short-term effects, it can progress to cirrhosis, hepatic decompensation, hepatocellular carcinoma (HCC), and death. The rate of new HCV infections is decreasing, yet the number of infected people with complications of the disease is increasing. In the United States, people born between 1945 and 1964 (baby boomers) are developing more complications of infection. Men and African Americans have a higher prevalence of HCV infection. Progression of fibrosis can be accelerated by factors such as older age, duration of HCV infection, sex, and alcohol intake. Furthermore, insulin resistance can cause hepatic steatosis and is associated with fibrosis progression and inflammation. If more effective therapies are not adopted for HCV, more than 1 million patients could develop HCV-related cirrhosis, hepatic decompensation, or HCC by 2020, which will impact the US health care system. It is important to recognize the impact of HCV on liver disease progression and apply new therapeutic strategies.

Role of placental growth factor in mesenteric neoangiogenesis in a mouse model of portal hypertension

BACKGROUND & AIMS

Portal hypertension is responsible for the major complications associated with cirrhosis. Angiogenesis has been associated with the pathophysiology of portal hypertension. We investigated the role of placental growth factor (PlGF) and tested the effects of monoclonal antibodies against PlGF (alphaPlGF) in a mouse model of portal hypertension.

METHODS

Using a mouse model of prehepatic portal hypertension, we measured PlGF levels in the mesenteric tissue at different time points. We used knockout mice and alphaPlGF to determine the role of PlGF in the splanchnic hyperdynamic system and portosystemic collateral formation, examining its effects before and after portal hypertension was induced.

RESULTS

PlGF was significantly up-regulated in the mesenteric tissue of mice with portal hypertension. Compared with wild-type animals, the vascular density in the mesentery was reduced in PlGF knockout hypertensive mice, preventing collateral formation and attenuation of mesenteric artery flow without affecting portal pressure. In the prevention study, alphaPlGF showed similar findings as in the knockout study. In mice with portal hypertension, administration of alphaPlGF resulted in a 32% decrease in portal pressure, compared with mice given immunoglobulin G(1) (control).

CONCLUSIONS

Pathologic angiogenesis in the mesenteric tissues of mice with portal hypertension is mediated by PlGF. Blocking PlGF could be an effective strategy for reducing collateral formation and lowering portal pressure; further research into the effects in cirrhosis is warranted.

Patients with chronic hepatitis B infection display deficiency of plasmacytoid dendritic cells with reduced expression of TLR9

Chronic hepatitis B virus (HBV) infection is a complex interaction between replicating noncytopathic virus and dysregulatory host antiviral immunity. Plasmacytoid dendritic cells (pDCs) contribute to innate antiviral immunity via secreting type I interferons. Toll-like receptor (TLR) 9 is involved in major pattern recognition receptors expressed in pDCs. The frequency of pDCs and TLR9 expression in peripheral blood mononuclear cells (PBMC) was determined, using flow cytometry. IFN-alpha production by PBMC was evaluated in vitro in the presence of cytidine phosphate guanosine (CpG) with/without pDCs. The correlation between TLR9, pDCs frequency and viral load was also evaluated. TLR9 expression in pDCs in chronic HBV patients was significantly ( approximately 50%) reduced, supported by approximately 70% reduction of TLR9 mRNA, in comparison to healthy controls, correlating with the impairment of IFN-alpha production in vitro. Furthermore, pDCs frequency in these patients was substantially reduced ( approximately 30%), inversely correlating with serum ALT levels and HBV viral load. HBsAg and HBcAg were detected by immunohistochemistry in pDCs in chronic HBV patients. We conclude that HBV infection results in reduced frequency of circulating pDCs and their functional impairment via inhibiting the expression of TLR9. These data may provide useful information in both basic research and clinical treatment of chronic HBV infection.