Nitric oxide promotes caspase-independent hepatic stellate cell apoptosis through the generation of reactive oxygen species

LPSF/GQ-02 inhibits the development of hepatic steatosis and inflammation in a mouse model of non-alcoholic fatty liver disease (NAFLD)

Non-alcoholic fatty liver disease (NAFLD) defines a wide spectrum of liver diseases that extends from simple steatosis to non-alcoholic steatohepatitis. Although the pathogenesis of NAFLD remains undefined, it is recognized that insulin resistance is present in almost all patients who develop this disease. Thiazolidinediones (TZDs) act as an insulin sensitizer and have been used in the treatment of patients with type 2 diabetes and other insulin-resistant conditions, including NAFLD. Hence, therapy of NAFLD with insulin-sensitizing drugs should ideally improve the key hepatic histological changes, while also reducing cardiometabolic and cancer risks. Controversially, TZDs are associated with the development of cardiovascular events and liver problems. Therefore, there is a need for the development of new therapeutic strategies to improve liver function in patients with chronic liver diseases. The aim of the present study was to assess the therapeutic effects of LPSF/GQ-02 on the liver of LDLR-/- mice after a high-fat diet. Eighty male mice were divided into 4 groups and two different experiments: 1-received a standard diet; 2-fed with a high-fat diet (HFD); 3–HFD+pioglitazone; 4–HFD+LPSF/GQ-02. The experiments were conducted for 10 or 12 weeks and in the last two or four weeks respectively, the drugs were administered daily by gavage. The results obtained with an NAFLD murine model indicated that LPSF/GQ-02 was effective in improving the hepatic architecture, decreasing fat accumulation, reducing the amount of collagen, decreasing inflammation by reducing IL-6, iNOS, COX-2 and F4 / 80, and increasing the protein expression of IκBα, cytoplasmic NFκB-65, eNOS and IRS-1 in mice LDLR -/-. These results suggest a direct action by LPSF/GQ-02 on the factors that affect inflammation, insulin resistance and fat accumulation in the liver of these animals. Further studies are being conducted in our laboratory to investigate the possible mechanism of action of LPSF/GQ-02 on hepatic lipid metabolism.

Endothelial Gab1 deficiency aggravates splenomegaly in portal hypertension independent of angiogenesis

Certain pathological changes, including angiogenesis, actively contribute to the pathogenesis of splenomegaly in portal hypertension (PH), although the detailed molecular and cellular mechanisms remain elusive. In this study, we demonstrated that endothelial Grb-2-associated binder 1 (Gab1) plays a negative role in PH-associated splenomegaly independent of angiogenesis. PH, which was induced by partial portal vein ligation, significantly enhanced Gab1 expression in endothelial cells in a time-dependent manner. Compared with controls, endothelium-specific Gab1 knockout (EGKO) mice exhibited a significant increase in spleen size while their PH levels remained similar. Pathological analysis indicated that EGKO mice developed more severe hyperactive white pulp and fibrosis in the enlarged spleen but less angiogenesis in both the spleen and mesenteric tissues. Mechanistic studies showed that the phosphorylation of endothelial nitric oxide synthase (eNOS) in EGKO mice was significantly lower than in controls. In addition, the dysregulation of fibrosis and inflammation-related transcription factors [e.g., Krüppel-like factor (KLF) 2 and KLF5] and the upregulation of cytokine genes (e.g., TNF-α and IL-6) were observed in EGKO mice. We thus propose that endothelial Gab1 mediates multiple pathways in inhibition of the pathogenesis of splenomegaly in PH via prevention of endothelial dysfunction and overproduction of proinflammatory/profibrotic cytokines.

Fibronectin peptides as potential regulators of hepatic fibrosis through apoptosis of hepatic stellate cells

The turnover of extracellular matrix (ECM) components can generate signals that regulate several cellular functions such as proliferation, differentiation, and apoptosis. During liver injury, matrix metalloproteases (MMPs) production is enhanced and increased levels of peptides derived from extracellular matrix proteins can be generated. Synthetic peptides with sequences present in extracellular matrix proteins were previously found to induce both stimulating and apoptotic effects on several cell types including the inflammatory cells monocytes/macrophages. Therefore, in inflammatory liver diseases, locally accumulated peptides could be also important in regulating hepatic fibrosis by inducing apoptosis of hepatic stellate cells (HSC), the primary cellular source of extracellular matrix components. Here, we describe the apoptotic effect of fibronectin peptides on the cell line of human hepatic stellate cells LX-2 based on oligonucleosomal DNA fragmentation, caspase-3 and -9 activation, Bcl-2 depletion, and accumulation of Bax protein. We also found that these peptides trigger the activation of Src kinase, which in turn mediated the increase of JNK and p38 activities. By the use of specific inhibitors we demonstrated the involvement of Src, JNK, and p38 in apoptosis induced by fibronectin peptides on HSC. Moreover, fibronectin peptides increased iNOS expression in human HSC, and specific inhibition of iNOS significantly reduced the sustained activity of JNK and the programmed cell death caused by these peptides. Finally, the possible regulatory effect of fibronectin peptides in liver fibrosis was further supported by the ability of these peptides to induce metalloprotease-9 (MMP-9) expression in human monocytes.

Vascular pathobiology in chronic liver disease and cirrhosis - current status and future directions

Chronic liver disease is associated with remarkable alterations in the intra- and extrahepatic vasculature. Because of these changes, the fields of liver vasculature and portal hypertension have recently become closely integrated within the broader vascular biology discipline. As developments in vascular biology have evolved, a deeper understanding of vascular processes has led to a better understanding of the mechanisms of the dynamic vascular changes associated with portal hypertension and chronic liver disease. In this context, hepatic vascular cells, such as sinusoidal endothelial cells and pericyte-like hepatic stellate cells, are closely associated with one another, where they have paracrine and autocrine effects on each other and themselves. These cells play important roles in the pathogenesis of liver fibrosis/cirrhosis and portal hypertension. Further, a variety of signaling pathways have recently come to light. These include growth factor pathways involving cytokines such as transforming growth factor β, platelet derived growth factor, and others as well as a variety of vasoactive peptides and other molecules. An early and consistent feature of liver injury is the development of an increase in intra-hepatic resistance; this is associated with changes in hepatic vascular cells and their signaling pathway that cause portal hypertension. A critical concept is that this process aggregates signals to the extrahepatic circulation, causing derangement in this system's cells and signaling pathways, which ultimately leads to the collateral vessel formation and arterial vasodilation in the splanchnic and systemic circulation, which by virtue of the hydraulic derivation of Ohm's law (pressure = resistance × flow), worsens portal hypertension. This review provides a detailed review of the current status and future direction of the basic biology of portal hypertension with a focus on the physiology, pathophysiology, and signaling of cells within the liver, as well as those in the mesenteric vascular circulation. Translational implications of recent research and the future directions that it points to are also highlighted.

iNSC suppress macrophage-induced inflammation by repressing COX-2

Brain inflammation causes cell damage and death in diseases such as Alzheimer's and Parkinson's. In this study, we investigated whether early induced neural stem cells (iNSCs) could protect against cell death after treatment with THP1-derived macrophages. We developed an inflammatory model system with THP1-derived macrophages and cortical neuronal cells and investigated the therapeutic efficacy of iNSC against macrophage-induced inflammation in this model. Apoptosis was confirmed by double immunocytochemistry with NeuN and 4',6-diamidino-2-phenylindole using terminal deoxynucleotidyl transferase-mediated digoxigenin-dUTP-biotin nick-end labeling. Cortical neuronal cells cultured with iNSCs exhibited fewer apoptotic cells than did cultures without iNSCs. The levels of inflammatory cytokines and vascular endothelial growth factor (VEGF) were analyzed by enzyme-linked immunosorbent assay. Cells cultured with iNSCs had lower levels of inflammatory cytokines and higher VEGF levels than those cultured without iNSCs. Western blot analysis for cyclooxygenase-2 (COX-2) showed a significantly lower level of COX-2 in cells cultured with iNSCs than in those cultured without iNSCs. Thus, early iNSCs administration reduced inflammation associated with neurological recovery, and this effect is mediated by COX-2 regulation. Our results suggest that iNSCs have potential therapeutic relevance, because they display strong anti-inflammatory functions that promote neuroprotection thorough the inflammatory response.

Peripheral vein infusion of autologous mesenchymal stem cells in Egyptian HCV-positive patients with end-stage liver disease

Introduction

We have assessed the utility of autologous mesenchymal stem cell (MSC) peripheral vein infusion as a possible therapeutic modality for patients with end-stage liver diseases.

Methods

Forty patients with post-hepatitis C virus (HCV) end-stage liver disease were randomized into two groups: Group 1 (GI): 20 patients who received granulocyte colony-stimulating factor (G-CSF) for 5 days followed by autologous MSCs peripheral-vein infusion and group 2 (GII): 20 patients who received regular liver-supportive treatment only (control group).

Results

In MSC-infused patients (GI), 54% showed near normalization of liver enzymes and improvement in liver synthetic function. Significant changes were reported in albumin (P = 0.000), bilirubin (P = 0.002), increased international normalized ratio (INR) (P = 0.017), prothrombin concentration (P = 0.029) and alanine transaminase (ALT) levels (P = 0.029), with stabilization of clinical and biochemical status in 13% of cases. None of the patients in GII showed any significant improvement. Hepatic fibrosis was assessed in GI by detection of procollagen IIIC peptide level (PIIICP) and procollagen III N peptide level (PIIINP). The pretreatment values of s-PIIICP and s-PIIINP were 9.4 ± 4.2 and 440 ± 189, respectively, with a decrease to 8.1 ± 2.6 and 388 ± 102, respectively, 3 months after MSC therapy. However, the difference was statistically nonsignificant (P = 0.7). A significant correlation coefficient was reported after 3 months between the s-PIIINP and prothrombin concentration (P = -0.5) and between s-PIIICP and ascites (P = 0.550).

Conclusions

First, autologous MSC infusion into a peripheral vein is as effective as the previously reported intrahepatic infusion. Second, MSCs have a supportive role in the treatment of end-stage liver disease, with satisfactory tolerability and beneficial effects on liver synthetic functions and hepatic fibrosis. Third, IV infusion of MSCs after G-CSF mobilization improves s-albumin within the first 2 weeks and prothrombin concentration and alanine Taransaminase after 1 month. According to the data from this current study and those previously reported by our group, we recommend further studies on patients’ infusion with pure CD133 and CD34 followed by IV infusion of in vitro-differentiated MSCs within 1 week and another infusion after 3 months.

Trial registration

ClinicalTrials.gov NCT01729221. Registered 17 November 2012.

In vitro interactions between rat bone marrow-derived endothelial progenitor cells and hepatic stellate cells: interaction between EPCs and HSCs

Transplantation of bone marrow (BM)-derived endothelial progenitor cells (EPCs) has been reported to improve liver fibrosis, but there is no direct evidence for the mechanism of improvement. We investigated the mechanism in vitro by coculturing BM-derived EPCs with activated hepatic stellate cells (HSCs) to mimic the hepatic environment. EPCs and HSCs were cultured alone and indirectly cocultured at a 1:1 ratio in a Transwell system. The characteristics of HSCs and EPCs were examined at different time points. An invasion assay showed the time-dependent effect on degradation of the extracellular matrix (ECM) layer in EPCs cultured alone. Real-time PCR and enzyme-linked immunosorbent assay analysis revealed that EPCs served as a source of matrix metalloproteinase-9 (MMP-9), and MMP-9 expression levels significantly increased during the 2 d of coculture. CFSE labeling showed that EPCs inhibited proliferation of HSCs. Annexin-V/PI staining, erminal deoxynucleotidyl transferase X-dUTP nick end labeling analysis, and (cleaved) caspase-3 activity revealed that EPCs promoted HSC apoptosis. However, the proliferation and apoptosis of EPCs were unaffected by cocultured HSCs. Coculturing increased the expression of inducible nitric oxide synthase, vascular endothelial growth factor, and hepatocyte growth factor (HGF) in EPCs, promoted differentiation of EPCs, and reduced the expression of types I and III collagens and transforming growth factor beta 1. Knockdown of HGF expression attenuated EPC-induced activation of HSC apoptosis and profibrotic ability. These findings demonstrated that BM-derived EPCs could degrade ECM, promoting activated HSC apoptosis, suppressing proliferation and profibrotic ability of activated HSCs. HGF secretion by EPCs plays a key role in inducing activated HSC apoptosis and HSC profibrotic ability.

Review of experimental models for inducing hepatic cirrhosis by bile duct ligation and carbon tetrachloride injection

PURPOSE

To present a review about a comparative study of bile duct ligation versus carbon tetrachloride Injection for inducing experimental liver cirrhosis.

METHODS

This research was made through Medline/PubMed and SciELO web sites looking for papers on the content "induction of liver cirrhosis in rats". We have found 107 articles but only 30 were selected from 2004 to 2011.

RESULTS

The most common methods used for inducing liver cirrhosis in the rat were administration of carbon tetrachloride (CCl4) and bile duct ligation (BDL). CCl4 has induced cirrhosis from 36 hours to 18 weeks after injection and BDL from seven days to four weeks after surgery.

CONCLUSION

For a safer inducing cirrhosis method BDL is better than CCl4 because of the absence of toxicity for researches and shorter time for achieving it.

Hepatic stellate cells and metastatic liver neoplasms

Hepatic stellate cells (HSCs) were first described in the 19th century as a type of multi-functional mesenchymal cells. They are considered as the component of liver microenvironment because of their capacity to differentiate into myofibroblasts which are highly proliferative and have collagen secretion capacity. This paper reviews the interactions between tumor cells and HSCs in liver microenvironment and discusses mechanisms by which tumor-derived factors activate HSCs, and in turn, activated HSC promotes metastatic tumor growth. The interactions between tumor cells and HSCs in liver microenvironment can be regarded as an "amplification loop". The activation of HSCs is a complex process that is regulated by multiple pathways, such as the transforming growth factor-β and platelet-derived growth factor signaling pathways. HSCs provide a possible therapeutic target for liver metastases to effectively increase the survival of patients.

Retinol binding protein-albumin domain III fusion protein deactivates hepatic stellate cells

Liver fibrosis is characterized by accumulation of extracellular matrix, and activated hepatic stellate cells (HSCs) are the primary source of the fibrotic neomatrix and considered as therapeutic target cells. We previously showed that albumin in pancreatic stellate cells (PSCs), the key cell type for pancreatic fibrogenesis, is directly involved in the formation of vitamin A-containing lipid droplets, inhibiting PSC activation. In this study, we evaluated the anti-fibrotic activity of both albumin and retinol binding protein-albumin domain III fusion protein (R-III), designed for stellate cell-targeted delivery of albumin III, in rat primary HSCs and investigated the underlying mechanism. Forced expression of albumin or R-III in HSCs after passage 2 (activated HSCs) induced lipid droplet formation and deactivated HSCs, whereas point mutations in high-affinity fatty acid binding sites of albumin domain III abolished their activities. Exogenous R-III, but not albumin, was successfully internalized into and deactivated HSC-P2. When HSCs at day 3 after plating (pre-activated HSCs) were cultured in the presence of purified R-III, spontaneous activation of HSCs was inhibited even after passage 2, suggestive of a potential for preventive effect. Furthermore, treatment of HSCs-P2 with R-III led to a significant reduction in both cytoplasmic levels of all-trans retinoic acid and the subsequent retinoic acid signaling. Therefore, our data suggest that albumin deactivates HSCs with reduced retinoic acid levels and that R-III may have therapeutic and preventive potentials on liver fibrosis.

The potential of microRNAs in liver fibrosis

MicroRNAs (miRNAs) are a class of ~22-nucleotides noncoding RNAs that regulate gene expression by specifically binding with 3'-untranslated region (3'-UTR) of target gene mRNAs to posttranscriptionally effect mRNA stability and translation,and play essential roles in a variety of biological processes, including cell development, proliferation, differentiation, and apoptosis. Liver fibrosis is the occurrence of liver cell necrosis and inflammatory stimulation, and is characterized by excessive accumulation of extracellular matrices(ECMs). In the fibrotic liver, hepatic stellate cells (HSCs), which are regulated by multiple signal transduction pathways, undergo myofibroblastic transdifferentiation and are generally regarded as the major ECM producer responsible for liver fibrosis. A growing body of evidence suggests that divergent miRNAs participate in liver fibrotic process and activation of HSC. Moreover, members of many signal transduction pathways are important targets for miRNAs. In this review, we make a summary on current understanding of the roles of miRNAs in the development of liver fibrosis, HSC functions and their potential as novel drug targets.

Ferric citrate CYP2E1-independently promotes alcohol-induced apoptosis in HepG2 cells via oxidative/nitrative stress which is attenuated by pretreatment with baicalin

In the case of alcoholic liver injury, an iron overload is always present. Both alcohol and iron can individually induce oxidative stress in liver. However, the combined effect of physiological concentrations of alcohol and iron on oxidative stress in hepatocytes remains unknown. Baicalin has been demonstrated to be an antioxidant or iron chelator in animal experiments. In this study, we investigated the injury to hepatocytes CYP2E1-independently induced by the combination of alcohol and iron and the protective effect of baicalin. Compared with cells treated with ethanol alone, ferric citrate enhanced the accumulation of reactive oxygen and nitrogen species, increased the occurrence of protein carbonylation/nitration and the levels of 4-hydroxy-2-nonenal, changed the distribution of iNOS, and eventually resulted in apoptosis. However, pretreatment with baicalin inhibited the oxidative stress induced by the combination of alcohol and iron, mainly by chelating iron. Our findings therefore suggest that iron could CPY2E1-independently enhance the oxidative stress induced by alcohol, which probably contributes to the pathogenesis of alcoholic liver disease. Baicalin is a promising phytomedicine for preventing alcoholic liver disease.

Nitric oxide augments mesenchymal stem cell ability to repair liver fibrosis

Background

Liver fibrosis is a major health problem worldwide and poses a serious obstacle for cell based therapies. Mesenchymal stem cells (MSCs) are multipotent and important candidate cells for future clinical applications however success of MSC therapy depends upon their homing and survival in recipient organs. This study was designed to improve the repair potential of MSCs by transplanting them in sodium nitroprusside (SNP) pretreated mice with CCl₄ induced liver fibrosis.

Methods

SNP 100 mM, a nitric oxide (NO) donor, was administered twice a week for 4 weeks to CCl₄-injured mice. MSCs were isolated from C57BL/6 wild type mice and transplanted in the left lateral lobe of the liver in experimental animals. After 4 weeks, animals were sacrificed and liver improvement was analyzed. Analysis of fibrosis by qRT-PCR and sirius red staining, homing, bilirubin and alkaline phosphatase (ALP) serum levels between different treatment groups were compared to control.

Results

Liver histology demonstrated enhanced MSCs homing in SNP-MSCs group compared to MSCs group. The gene expression of fibrotic markers; αSMA, collagen 1α1, TIMP, NFκB and iNOS was down regulated while cytokeratin 18, albumin and eNOS was up-regulated in SNP-MSCs group. Combine treatment sequentially reduced fibrosis in SNP-MSCs treated liver compared to the other treatment groups. These results were also comparable with reduced serum levels of bilirubin and ALP observed in SNP-MSCs treated group.

Conclusion

This study demonstrated that NO effectively augments MSC ability to repair liver fibrosis induced by CCl₄ in mice and therefore is a better treatment regimen to reduce liver fibrosis.

Glycosylated diazeniumdiolate-based oleanolic acid derivatives: synthesis, in vitro and in vivo biological evaluation as anti-human hepatocellular carcinoma agents

A series of O(2)-glycosylated diazeniumdiolate-based derivatives of oleanolic acid (4-19) were synthesized and their anti-human hepatocellular carcinoma (HCC) activities were evaluated. Compound 6 selectively inhibited HCC, but not non-tumor liver cell proliferation. This inhibition was attributed to high levels of nitric oxide (NO) released in HCC cells. Importantly, 6 exhibited low acute toxicity (LD(50) = 173.3 mg kg(-1)) and potent inhibition of HCC tumor growth in mice (3 mg kg(-1) iv). Furthermore, 6 induced HCC cell apoptosis, which was accompanied by lower mitochondrial membrane potentials and Bcl2 expression, but with higher cytochrome C release, Bax, caspase 3 and 9 expression activities in HCC cells. Collectively, 6 may be a promising candidate drug for the intervention of HCC.

Sinusoidal endothelial dysfunction precedes inflammation and fibrosis in a model of NAFLD

Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of the metabolic syndrome. Most morbidity associated with the metabolic syndrome is related to vascular complications, in which endothelial dysfunction is a major pathogenic factor. However, whether NAFLD is associated with endothelial dysfunction within the hepatic vasculature is unknown. The aims of this study were to explore, in a model of diet-induced overweight that expresses most features of the metabolic syndrome, whether early NAFLD is associated with liver endothelial dysfunction. Wistar Kyoto rats were fed a cafeteria diet (CafD; 65% of fat, mostly saturated) or a control diet (CD) for 1 month. CafD rats developed features of the metabolic syndrome (overweight, arterial hypertension, hypertryglyceridemia, hyperglucemia and insulin resistance) and liver steatosis without inflammation or fibrosis. CafD rats had a significantly higher in vivo hepatic vascular resistance than CD. In liver perfusion livers from CafD rats had an increased portal perfusion pressure and decreased endothelium-dependent vasodilation. This was associated with a decreased Akt-dependent eNOS phosphorylation and NOS activity. In summary, we demonstrate in a rat model of the metabolic syndrome that shows features of NAFLD, that liver endothelial dysfunction occurs before the development of fibrosis or inflammation.

Mechanisms and biomarkers of apoptosis in liver disease and fibrosis

Liver fibrosis and cirrhosis are a major cause of morbidity and mortality worldwide. Development of the fibrotic scar is an outcome of chronic liver diseases of varying aetiologies including alcoholic liver disease (ALD) nonalcoholic liver disease (NAFLD) including non-alcoholic steatohepatitis (NASH) viral hepatitis B and C (HBV, HCV). The critical step in the development of scar is activation of hepatic stellate cells (HSCs), which become the primary source of extracellular matrix. Aberrant apoptosis is a feature of chronic liver diseases and is associated with worsening stages of fibrosis. However, apoptosis is also the main mechanism promoting the resolution of fibrosis, and spontaneous or targeted apoptosis of HSC is associated with regression of fibrosis in animal models and patients with chronic liver disease. Given the importance of apoptosis in disease progression and resolution, there is much interest in precisely delineating the mechanisms involved and also developing biomarkers that accurately reflect the underlying pathogenesis. Here, we review the mechanisms driving apoptosis in development of liver disease and use of apoptosis -related biomarkers to aid in clinical diagnosis. Finally, we will also examine the recent literature regarding new insights into mechanisms involved in apoptosis of activated HSCs as possible method of fibrosis regression.

Sinusoidal endothelial dysfunction precedes inflammation and fibrosis in a model of NAFLD

Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of the metabolic syndrome. Most morbidity associated with the metabolic syndrome is related to vascular complications, in which endothelial dysfunction is a major pathogenic factor. However, whether NAFLD is associated with endothelial dysfunction within the hepatic vasculature is unknown. The aims of this study were to explore, in a model of diet-induced overweight that expresses most features of the metabolic syndrome, whether early NAFLD is associated with liver endothelial dysfunction. Wistar Kyoto rats were fed a cafeteria diet (CafD; 65% of fat, mostly saturated) or a control diet (CD) for 1 month. CafD rats developed features of the metabolic syndrome (overweight, arterial hypertension, hypertryglyceridemia, hyperglucemia and insulin resistance) and liver steatosis without inflammation or fibrosis. CafD rats had a significantly higher in vivo hepatic vascular resistance than CD. In liver perfusion livers from CafD rats had an increased portal perfusion pressure and decreased endothelium-dependent vasodilation. This was associated with a decreased Akt-dependent eNOS phosphorylation and NOS activity. In summary, we demonstrate in a rat model of the metabolic syndrome that shows features of NAFLD, that liver endothelial dysfunction occurs before the development of fibrosis or inflammation.

Pathophysiology of portal hypertension and esophageal varices

Esophageal varices are the major complication of portal hypertension. It is detected in about 50% of cirrhosis patients, and approximately 5-15% of cirrhosis patients show newly formed varices or worsening of varices each year. The major therapeutic strategy of esophageal varices consists of primary prevention, treatment for bleeding varices, and secondary prevention, which are provided by pharmacological, endoscopic, interventional and surgical treatments. Optimal management of esophageal varices requires a clear understanding of the pathophysiology and natural history. In this paper, we outline the current knowledge and future prospect in the pathophysiology of esophageal varices and portal hypertension.

Insulin resistance and liver microcirculation in a rat model of early NAFLD

BACKGROUND & AIMS

Insulin contributes to vascular homeostasis in peripheral circulation, but the effects of insulin in liver microvasculature have never been explored. The aim of this study was to assess the vascular effects of insulin in the healthy and fatty liver.

METHODS

Wistar rats were fed a control or a high fat diet (HFD) for 3days, while treated with a placebo, the insulin-sensitizer metformin, or the iNOS inhibitor 1400W. Vascular responses to insulin were evaluated in the isolated liver perfusion model. Insulin sensitivity at the sinusoidal endothelium was tested by endothelium-dependent vasodilation in response to acetylcholine in the presence or absence of insulin and by the level of liver P-eNOS after an insulin injection.

RESULTS

Rats from the HFD groups developed liver steatosis. Livers from the control group showed a dose-dependent hepatic vasodilation in response to insulin, which was blunted in livers from HFD groups. Metformin restored liver vascular insulin-sensitivity. Pre-treatment with insulin enhanced endothelium-dependent vasodilation of the hepatic vasculature and induced hepatic eNOS phosphorylation in control rats but not in HFD rats. Treatment with metformin or 1400W restored the capacity of insulin to enhance endothelium dependent vasodilation and insulin induced eNOS phosphorylation in HFD rats.

CONCLUSIONS

The administration of a HFD induces insulin resistance in the liver sinusoidal endothelium, which is mediated, at least in part, through iNOS upregulation and can be prevented by the administration of metformin. Insulin resistance at the hepatic vasculature can be detected earlier than inflammation or any other sign of advanced NALFD.

miRNA studies in in vitro and in vivo activated hepatic stellate cells

AIM

To understand which and how different miRNAs are implicated in the process of hepatic stellate cell (HSC) activation.

METHODS

We used microarrays to examine the differential expression of miRNAs during in vitro activation of primary HSCs (pHSCs). The transcriptome changes upon stable transfection of rno-miR-146a into an HSC cell line were studied using cDNA microarrays. Selected differentially regulated miRNAs were investigated by quantitative real-time polymerase chain reaction during in vivo HSC activation. The effect of miRNA mimics and inhibitor on the in vitro activation of pHSCs was also evaluated.

RESULTS

We found that 16 miRNAs were upregulated and 26 were downregulated significantly in 10-d in vitro activated pHSCs in comparison to quiescent pHSCs. Overexpression of rno-miR-146a was characterized by marked upregulation of tissue inhibitor of metalloproteinase-3, which is implicated in the regulation of tumor necrosis factor-α activity. Differences in the regulation of selected miRNAs were observed comparing in vitro and in vivo HSC activation. Treatment with miR-26a and 29a mimics, and miR-214 inhibitor during in vitro activation of pHSCs induced significant downregulation of collagen type I transcription.

CONCLUSION

Our results emphasize the different regulation of miRNAs in in vitro and in vivo activated pHSCs. We also showed that miR-26a, 29a and 214 are involved in the regulation of collagen type I mRNA.

miRNA studies in in vitro and in vivo activated hepatic stellate cells

AIM

To understand which and how different miRNAs are implicated in the process of hepatic stellate cell (HSC) activation.

METHODS

We used microarrays to examine the differential expression of miRNAs during in vitro activation of primary HSCs (pHSCs). The transcriptome changes upon stable transfection of rno-miR-146a into an HSC cell line were studied using cDNA microarrays. Selected differentially regulated miRNAs were investigated by quantitative real-time polymerase chain reaction during in vivo HSC activation. The effect of miRNA mimics and inhibitor on the in vitro activation of pHSCs was also evaluated.

RESULTS

We found that 16 miRNAs were upregulated and 26 were downregulated significantly in 10-d in vitro activated pHSCs in comparison to quiescent pHSCs. Overexpression of rno-miR-146a was characterized by marked upregulation of tissue inhibitor of metalloproteinase-3, which is implicated in the regulation of tumor necrosis factor-α activity. Differences in the regulation of selected miRNAs were observed comparing in vitro and in vivo HSC activation. Treatment with miR-26a and 29a mimics, and miR-214 inhibitor during in vitro activation of pHSCs induced significant downregulation of collagen type I transcription.

CONCLUSION

Our results emphasize the different regulation of miRNAs in in vitro and in vivo activated pHSCs. We also showed that miR-26a, 29a and 214 are involved in the regulation of collagen type I mRNA.

Hepatic stellate cells: partners in crime for liver metastases?

Hepatic stellate cells (HSCs) were recently postulated as a component of the prometastatic liver microenvironment, because they can transdifferentiate into highly proliferative and motile myofibroblasts that are implicated in the desmoplastic reaction and metastatic growth. This review focuses on bidirectional interactions between tumor cells and HSCs in the liver microenvironment and discusses mechanisms whereby tumor-derived factors activate HSCs, and in turn, activated HSCs promote metastatic growth. Bidirectional interactions between tumors and HSCs may function as an "amplification loop" to further enhance metastatic growth in the liver. The activation of HSCs is a complex process regulated by multiple factors such as transforming growth factor-β and platelet-derived growth factor signaling pathways, which may present as therapeutic targets in the prevention and treatment of liver metastases.

CONCLUSION

HSCs may present a new therapeutic target in the treatment of liver metastases. Targeting HSCs and/or myofibroblasts with transforming growth factor-β or platelet-derived growth factor antagonists in coordination with chemotherapy, radiotherapy, or surgery may prove to be effective at reducing liver metastases and increasing the survival benefit of patients by targeting both tumor cells and the tumor microenvironment.

S-Nitroso-N-acetylcysteine induces de-differentiation of activated hepatic stellate cells and promotes antifibrotic effects in vitro

Nitric oxide (NO) has been shown to act as a potent antifibrogenic agent by decreasing myofibroblast differentiation. S-Nitroso-N-acetylcysteine (SNAC), a NO donor, attenuates liver fibrosis in rats, but the cellular and molecular mechanisms on liver myofibroblast-like phenotype still remain unknown. Here, we investigate the antifibrotic effects of SNAC on hepatic stellate cells, the major fibrogenic cell type in the liver. A murine GRX cell line was incubated with SNAC (100μM) or vehicle (control group) for 72h. Cell viability was measured by MTT colorimetric assay and the conversion of myofibroblast into quiescent fat-storing cell phenotype was evaluated by Oil-Red-O staining. TGFβ-1, TIMP-1, and MMP-13 levels were measure in the supernatant by ELISA. Profibrogenic- and fibrolytic-related gene expression was quantified using real-time qPCR. SNAC induced phenotype conversion of myofibroblast-like phenotype into quiescent cells. SNAC decreased gene and protein expression of TGFβ-1 and MMP-2 compared to control groups. Besides, SNAC down-regulated profibrogenic molecules and up-regulated MMP-13 gene expression, which plays a key role in the degradation of interstitial collagen in liver fibrosis. In conclusion, these findings demonstrate that SNAC efficiently can modulate the activation and functionality of murine hepatic stellate cells and could be considered as an antifibrotic treatment to human liver fibrosis.

Glycogen synthase kinase-3 (GSK-3) inhibition attenuates hepatocyte lipoapoptosis

BACKGROUNDS & AIMS

Saturated free fatty acids induce hepatocyte lipoapoptosis, a key pathologic feature of non-alcoholic steatohepatitis. The saturated free fatty acid palmitate induces hepatocyte lipoapoptosis via an endoplasmic reticulum stress pathway resulting in c-Jun-N-terminal (JNK) activation. Glycogen synthase kinase (GSK)-3 is a serine/threonine kinase which may also promote JNK activation. Thus, our aim was to determine if GSK-3 inhibition suppresses palmitate induced JNK activation and lipoapoptosis.

METHODS

For these studies, we employed mouse primary hepatocytes, Huh-7 and Hep3B cell lines.

RESULTS

Palmitate-induced GSK-3 activation was identified by phosphorylation of its substrate glycogen synthase. GSK-3 pharmacologic inhibition, by GSK-3 inhibitor IX and enzastaurin, significantly reduced PA-mediated lipoapoptosis. More importantly, Huh-7 cells, in which either GSK-3α or GSK-3β isoforms were stably and selectively knocked down by shRNA, displayed resistance to palmitate-induced cytotoxicity. GSK-3 pharmacological inhibitors and shRNA-targeted knockdown of GSK-3α or GSK-3β also suppressed JNK activation by palmitate. JNK activation, in part, promotes lipoapotosis by inducing expression of the pro-apoptotic effector p53-upregulated modulator of apoptosis (PUMA). Consistent with this concept, GSK-3 pharmacologic inhibition also reduced PUMA cellular protein levels during exposure to palmitate. On the other hand, the GSK-3 inhibitors did not prevent PA induction of ER stress.

CONCLUSIONS

Our results suggest that GSK-3 activation promotes a JNK-dependent cytotoxic signaling cascade culminating in lipoapoptosis.

Protein kinase G signaling disrupts Rac1-dependent focal adhesion assembly in liver specific pericytes

Nitric oxide (NO) regulates the function of perivascular cells (pericytes), including hepatic stellate cells (HSC), mainly by activating cGMP and cGMP-dependent kinase (PKG) via NO/cGMP paracrine signaling. Although PKG is implicated in integrin-mediated cell adhesion to extracellular matrix, whether or how PKG signaling regulates the assembly of focal adhesion complexes (FA) and migration of HSC is not known. With the help of complementary molecular and cell biological approaches, we demonstrate here that activation of PKG signaling in HSC inhibits vascular tubulogenesis, migration/chemotaxis, and assembly of mature FA plaques, as assessed by vascular tubulogenesis assays and immunofluorescence localization of FA markers such as vinculin and vasodilator-stimulated phosphoprotein (VASP). To determine whether PKG inhibits FA assembly by phosphorylation of VASP at Ser-157, Ser-239, and Thr-278, we mutated these putative phosphorylation sites to alanine (VASP3A, phosphoresistant mutant) or aspartic acid (VASP3D, phosphomimetic), respectively. Data generated from these two mutants suggest that the effect of PKG on FA is independent of these three phosphorylation sites. In contrast, activation of PKG inhibits the activity of small GTPase Rac1 and its association with the effector protein IQGAP1. Moreover, PKG activation inhibits the formation of a trimeric protein complex containing Rac1, IQGAP1, and VASP. Finally, we found that expression of a constitutively active Rac1 mutant abolishes the inhibitory effects of PKG on FA formation. In summary, our data suggest that activation of PKG signaling in pericytes inhibits FA formation by inhibiting Rac1.

Nitric oxide is the primary mediator of cytotoxicity induced by GSH depletion in neuronal cells

Glutathione (GSH) levels progressively decline during aging and in neurodegenerative disorders. However, the contribution of such event in mediating neuronal cell death is still uncertain. In this report, we show that, in neuroblastoma cells as well as in primary mouse cortical neurons, GSH decrease, induced by buthionine sulfoximine (BSO), causes protein nitration, S-nitrosylation and DNA strand breaks. Such alterations are also associated with inhibition of cytochrome c oxidase activity and microtubule network disassembly, which are considered hallmarks of nitric oxide (NO) toxicity. In neuroblastoma cells, BSO treatment also induces cell proliferation arrest through the ERK1/2-p53 pathway that finally results in caspase-independent apoptosis, as evident from the translocation of apoptosis-inducing factor from mitochondria towards nuclei. A deeper analysis of the signaling processes indicates that the NO-cGMP pathway is involved in cell proliferation arrest and death. In fact, these events are completely reversed by L-NAME, a specific NO synthase inhibitor, indicating that NO, rather than the depletion of GSH per se, is the primary mediator of cell damage. In addition, the guanylate cyclase (GC) inhibitor LY83583 is able to completely block activation of ERK1/2 and counteract BSO toxicity. In cortical neurons, NMDA (N-methyl-D-aspartic acid) treatment results in GSH decrease and BSO-mediated NO cytotoxicity is enhanced by either epidermal growth factor (EGF) or NMDA. These findings support the idea that GSH might represent the most important buffer of NO toxicity in neuronal cells, and indicate that the disruption of cellular redox buffering controlled by GSH makes neuronal cells susceptible to endogenous physiological flux of NO.

Intrahepatic angiogenesis and sinusoidal remodeling in chronic liver disease: new targets for the treatment of portal hypertension?

Portal hypertension accounts for the majority of morbidity and mortality that is encountered in patients with cirrhosis. Portal hypertension is initiated in large part through increases in intrahepatic vascular resistance. Fibrosis, regenerative nodule formation, and intrahepatic vasoconstriction are classical mechanisms that account for increased intrahepatic vascular resistance in cirrhosis. Recent data suggest that intrahepatic angiogenesis and sinusoidal remodeling could also be involved in sinusoidal resistance, fibrosis, and portal hypertension. While angiogenesis is defined as the formation of new vessels deriving from existing ones, sinusoidal remodeling in its pathological form associated with cirrhosis is characterized by increased mural coverage of vessels by contractile HSC. Most attention on the mechanisms of these processes has focused on the liver sinusoidal endothelial cell (SEC), the hepatic stellate cell (HSC), and the paracrine signaling pathways between these two cell types. Interventions that target these vascular structural changes have beneficial effects on portal hypertension and fibrosis in some animal studies which has stimulated interest for pursuing parallel studies in humans with portal hypertension.

Inhibition of VEGF- and NO-dependent angiogenesis does not impair liver regeneration

Angiogenesis occurs through a convergence of diverse signaling mechanisms with prominent pathways that include autocrine effects of endothelial nitric oxide (NO) synthase (eNOS)-derived NO and vascular endothelial growth factor (VEGF). However, the redundant and distinct roles of NO and VEGF in angiogenesis remain incompletely defined. Here, we use the partial hepatectomy model in mice genetically deficient in eNOS to ascertain the influence of eNOS-derived NO on the angiogenesis that accompanies liver regeneration. While sinusoidal endothelial cell (SEC) eNOS promotes angiogenesis in vitro, surprisingly the absence of eNOS did not influence the angiogenesis that occurs after partial hepatectomy in vivo. While this observation could not be attributed to induction of alternate NOS isoforms, it was associated with induction of VEGF signaling as evidenced by enhanced levels of VEGF ligand in regenerating livers from mice genetically deficient in eNOS. However, surprisingly, mice that were genetically heterozygous for deficiency in the VEGF receptor, fetal liver kinase-1, also maintained unimpaired capacity for liver regeneration. In summary, inhibition of VEGF- and NO-dependent angiogenesis does not impair liver regeneration, indicating signaling redundancies that allow liver regeneration to continue in the absence of this canonical vascular pathway.

p130Cas, Crk-associated substrate plays essential roles in liver development by regulating sinusoidal endothelial cell fenestration

p130Cas, Crk-associated substrate (Cas), is an adaptor/scaffold protein that plays a central role in actin cytoskeletal reorganization. We previously showed that mice in which Cas was deleted (Cas(-/-)) died in utero because of early cardiovascular maldevelopment. To further investigate the in vivo roles of Cas, we generated mice with a hypomorphic Cas allele lacking the exon 2-derived region (Cas(Deltaex2/Deltaex2)), which encodes Src homology domain 3 (SH3) of Cas. Cas(Deltaex2/Deltaex2) mice again died as embryos, but they particularly showed progressive liver degeneration with hepatocyte apoptosis. Because Cas expression in the liver is preferentially detected in sinusoidal endothelial cells (SECs), the observed hepatocyte apoptosis was most likely ascribable to impaired function of SECs. To address this possibility, we stably introduced a Cas mutant lacking the SH3 domain (Cas DeltaSH3) into an SEC line (NP31). Intriguingly, the introduction of Cas DeltaSH3 induced a loss of fenestrae, the characteristic cell-penetrating pores in SECs that serve as a critical route for supplying oxygen and nutrients to hepatocytes. The disappearance of fenestrae in Cas DeltaSH3-expressing cells was associated with an attenuation of actin stress fiber formation, a marked reduction in tyrosine phosphorylation of Cas, and defective binding of Cas to CrkII.

CONCLUSION

Cas plays pivotal roles in liver development through the reorganization of the actin cytoskeleton and formation of fenestrae in SECs.

Fabrication and characterization of an inorganic gold and silica nanoparticle mediated drug delivery system for nitric oxide

Nitric oxide (NO) plays an important role in inhibiting the development of hepatic fibrosis and its ensuing complication of portal hypertension by inhibiting human hepatic stellate cell (HSC) activation. Here we have developed a gold nanoparticle and silica nanoparticle mediated drug delivery system containing NO donors, which could be used for potential therapeutic application in chronic liver disease. The gold nanoconjugates were characterized using several physico-chemical techniques such as UV-visible spectroscopy and transmission electron microscopy. Silica nanoconjugates were synthesized and characterized as reported previously. NO released from gold and silica nanoconjugates was quantified under physiological conditions (pH = 7.4 at 37 degrees C) for a substantial period of time. HSC proliferation and the vascular tube formation ability, manifestations of their activation, were significantly attenuated by the NO released from these nanoconjugates. This study indicates that gold and silica nanoparticle mediated drug delivery systems for introducing NO could be used as a strategy for the treatment of hepatic fibrosis or chronic liver diseases, by limiting HSC activation.

Neuropilin-1 promotes cirrhosis of the rodent and human liver by enhancing PDGF/TGF-beta signaling in hepatic stellate cells

PDGF-dependent hepatic stellate cell (HSC) recruitment is an essential step in liver fibrosis and the sinusoidal vascular changes that accompany this process. However, the mechanisms that regulate PDGF signaling remain incompletely defined. Here, we found that in two rat models of liver fibrosis, the axonal guidance molecule neuropilin-1 (NRP-1) was upregulated in activated HSCs, which exhibit the highly motile myofibroblast phenotype. Additionally, NRP-1 colocalized with PDGF-receptor beta (PDGFRbeta) in HSCs both in the injury models and in human and rat HSC cell lines. In human HSCs, siRNA-mediated knockdown of NRP-1 attenuated PDGF-induced chemotaxis, while NRP-1 overexpression increased cell motility and TGF-beta-dependent collagen production. Similarly, mouse HSCs genetically modified to lack NRP-1 displayed reduced motility in response to PDGF treatment. Immunoprecipitation and biochemical binding studies revealed that NRP-1 increased PDGF binding affinity for PDGFRbeta-expressing cells and promoted downstream signaling. An NRP-1 neutralizing Ab ameliorated recruitment of HSCs, blocked liver fibrosis in a rat model of liver injury, and also attenuated VEGF responses in cultured liver endothelial cells. In addition, NRP-1 overexpression was observed in human specimens of liver cirrhosis caused by both hepatitis C and steatohepatitis. These studies reveal a role for NRP-1 as a modulator of multiple growth factor targets that regulate liver fibrosis and the vascular changes that accompany it and may have broad implications for liver cirrhosis and myofibroblast biology in a variety of other organ systems and disease conditions.

Paediatric cholestatic liver disease: Diagnosis, assessment of disease progression and mechanisms of fibrogenesis

Cholestatic liver disease causes significant morbidity and mortality in children. The diagnosis and management of these diseases can be complicated by an inability to detect early stages of fibrosis and a lack of adequate interventional therapy. There is no single gold standard test that accurately reflects the presence of liver disease, or that can be used to monitor fibrosis progression, particularly in conditions such as cystic fibrosis. This has lead to controversy over how suspected liver disease in children is detected and diagnosed. This review discusses the challenges in using commonly available methods to diagnose hepatic fibrosis and monitor disease progression in children with cholestatic liver disease. In addition, the review examines the mechanisms hypothesised to be involved in the development of hepatic fibrogenesis in paediatric cholestatic liver injury which may ultimately aid in identifying new modalities to assist in both disease detection and therapeutic intervention.

Thiol redox systems and protein kinases in hepatic stellate cell regulatory processes

Hepatic stellate cells (HSC) are the major producers of collagen in the liver and their conversion from resting cells to a proliferating, contractile and fibrogenic phenotype ('activation') is a critical step, leading to liver fibrosis characterized by deposition of excessive extracellular matrix. Cytokines, growth factors, reactive oxygen and nitrogen species (ROS/RNS), lipid peroxides and their products deriving from hepatocytes, Kupffer cells and other cells converge on HSC and influence their activation. This review focuses on glutathione and thioredoxin pathways, with particular emphasis on their role in HSC. These two systems have been shown to act in the metabolism of hydrogen peroxide, control of thiol redox balance and regulation of signalling pathways. Particular attention is paid to mitochondria and NADPH oxidase. Detailed knowledge of specific signalling, redox conditions and apoptotic processes will be of help in devising proper pharmacological treatments for liver fibrosis.

Apoptosis of hepatic stellate cells (HSC-T6) induced by sodium nitroprusside and mechanisms involved

AIM: To investigate whether nitric oxide (NO) donor sodium nitroprusside (SNP) can induce the apoptosis of hepatic stellate cells (HSC-T6) and to explore potential mechanisms involved.

METHODS: The apoptosis of HSC-T6 cells was determined by flow cytometry and Hoechst staining. The nuclear translocation of nuclear factor-κB (NF-κB) p65 was detected by laser scanning confocal microscopy. The expression of tissue inhibitor of matrix metalloproteinase-1 (TIMP-1), type I procollagen (procollagen I), and growth arrest and DNA damage-inducible protein (GADD45β) mRNAs was detected by real-time reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS: The apoptosis rate was significantly higher in HSC-T6 cells treated with SNP than in control cells (20.78% ± 5.91%vs 3.25% ± 1.26%, P = 0.031). Apoptotic HSC-T6 cells showed dense nuclear staining or granular fluorescence after Hoechst staining. Tumor necrosis factor-α (TNF-α)-mediated nuclear translocation of NF-κB p65 was inhibited by SNP treatment. With the increase in SNP dose, the expression levels of TIMP-1, procollagen I and GADD45β mRNAs were reduced (all P < 0.05).

CONCLUSION: SNP can induce the apoptosis of HSC-T6 cells and reduce the expression of TIMP-1 and procollagen I mRNAs perhaps by inhibiting NF-κB activity and reducing GADD45β mRNA expression.

Inhibition of aldose reductase attenuates endotoxin signals in human non-pigmented ciliary epithelial cells

Chronic inflammatory diseases such as autoimmune and bacterial infections are associated with an elevated risk of ocular inflammation. Ciliary epithelial cells that play an important role in maintaining aqueous humor dynamics and homeostasis of anterior segment of eye are continuously exposed to inflammatory markers during infections and injury. Lipopolysacchharide (LPS), a Gram-negative bacterial endotoxin, dysregulates aqueous humor (AqH) homeostasis by inducing inflammatory changes. We have investigated how inhibition of a polyol pathway enzyme, aldose reductase (AR), alters LPS-induced inflammatory changes in human non-pigmented ciliary epithelial cells (hNPECs). The stimulation of hNPECs with LPS (1 microg/ml) caused increased secretion of inflammatory markers such as PGE(2) and NO in the culture medium as well as increased expression of COX-2 and iNOS proteins in cell extracts. LPS also increased phosphorylation of MAPKs (ERK1/2) and SAPK/JNK and activation of redox-sensitive transcription factors NF-kappaB and AP-1 in hNPECs and inhibition of AR by zopolrestat and sorbinil ameliorated these changes. Further, LPS-induced decrease in the expression of Na/K-ATPase in hNPECs was restored by AR inhibitors. Similar results were observed in ciliary bodies of LPS-injected rats. Taken together, our results suggest that AR plays an important role in the LPS-induced inflammatory changes in hNPECs and that inhibition of AR could be a novel therapeutic approach for ocular inflammation.

Antifibrotic effects of ZK14, a novel nitric oxide-donating biphenyldicarboxylate derivative, on rat HSC-T6 cells and CCl4-induced hepatic fibrosis

AIM

To study the pharmacologic effect of ZK(14), a novel nitric oxide-donating biphenyldicarboxylate (DDB) derivative, on HSC-T6 cells and on CCl(4)-induced hepatic fibrosis.

METHODS

Inhibition of HSC-T6 cell growth by ZK(14) was evaluated by MTT assay. The effect of ZK(14) on the percentage of HSC-T6 cells undergoing apoptosis was measured using Annexin-V/PI double-staining and TUNEL assay. Mitochondrial membrane potential (MMP) and caspase activities were tested. Hepatic fibrosis was induced in Sprague-Dawley rats by intraperitoneal injection with 14% CCl(4). Rats with hepatic fibrosis were randomly divided into four groups: model control, ZK(14) (20 mg/kg), ZK(14) (10 mg/kg) and DDB (5 mg/kg). Levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), hyaluronic acid (HA), type III collagen (PCIII), and nitric oxide (NO) were assessed, and liver samples were stained with hematoxylin-eosin. The NO level in cells treated with ZK(14) in vitro was also measured.

RESULTS

The effect of ZK(14) on HSC-T6 cell apoptosis was concentration- and time-dependent, with up to 50% of cells becoming apoptotic when exposed to 100 mumol/L ZK(14) for 18 h. ZK(14) treatment resulted in mitochondrial membrane depolarization and activation of caspases 3 and 9. At a dose of 20 mg/kg, ZK(14) significantly decreased serum transaminase (AST, ALT) activities and fibrotic index (HA, PCIII) levels and significantly inhibited fibrogenesis.

CONCLUSION

These data indicate that ZK(14), a novel NO-donating DDB derivative, promotes HSC-T6 apoptosis in vitro through a signaling mechanism involving mitochondria and caspase activation and it inhibits CCl(4)-induced hepatic fibrosis in vivo. The results suggest that ZK(14) has potential therapeutic value in the treatment of hepatic fibrosis.

Changes in microRNAs associated with hepatic stellate cell activation status identify signaling pathways

Activation of hepatic stellate cells (HSCs), which is regulated by multiple signal transduction pathways, is the key event in liver fibrosis. Moreover, members of these pathways are important targets for microRNAs (miRNAs). To better understand the critical pathways of HSC activation, we performed comprehensive comparative bioinformatics analysis of microarrays of quiescent and activated HSCs. Changes in miRNAs associated with HSC activation status revealed that 13 pathways were upregulated and 22 pathways were downregulated by miRNA. Furthermore, mitochondrial integrity, based on highly upregulated Bcl-2 and downregulated caspase-9, was confirmed in HSCs and fibrotic livers by immnofluorescence assay, quantitative RT-PCR, and western blot analysis. These findings provide in vitro and in vivo evidence that the mitochondrial pathway of apoptosis plays a significant role in the progression of liver fibrogenesis via HSC activation.

Heat shock protein 90 inhibitor induces apoptosis and attenuates activation of hepatic stellate cells

Activated hepatic stellate cells (HSCs) are major participants in hepatic fibrosis; thus, the induction of HSC apoptosis has been proposed as an antifibrotic treatment strategy. Heat shock protein (Hsp) 90 is a molecular chaperone that stabilizes major signal transduction proteins, and its inhibitors have antitumor activity. In this study, the susceptibility of HSCs to an Hsp90 inhibitor was evaluated. LX-2 cells, an immortalized human HSC line, 17-(allylamino)-17-demethoxygeldanamycin (17AAG), an Hsp90 inhibitor, and monensin, an acidic sphingomyelinase inhibitor, were used in this study. Cellular apoptosis was quantified by 4',6-diamidino-2-phenylindole dihydrochloride staining, and signaling cascades were explored using immunoblotting and immunoprecipitation techniques. Nuclear factor (NF) kappaB activities were evaluated by immunofluorescent microscopy and enzyme-linked immunosorbent assay. Collagen alpha1 and alpha-smooth muscle actin expressions were determined by real-time reverse transcription-polymerase chain reaction and immunoblotting, respectively. It was found that 17AAG induced HSC apoptosis and that caspase 8 cleavage preceded the downstream activation of apoptotic signaling cascades. Furthermore, this caspase 8 activation was dependent on ceramide generation by acidic sphingomyelinase. In addition, 17AAG prevented NFkappaB nuclear translocation and activation, specifically by inducing complex formation between NFkappaB and the glucocorticoid receptor. In accordance, NFkappaB-dependent cellular FLICE-like inhibitory protein expression level was found to be reduced by 17AAG. Finally, 17AAG down-regulated collagen alpha1 and alpha-smooth muscle actin expression levels in HSCs before inducing apoptosis. These results demonstrate that the Hsp90 inhibitor induces HSC apoptosis via a sphingomyelinase- and NFkappaB-dependent mechanism. Because this inhibitor also reduces HSC activation before apoptosis, Hsp90 inhibitor treatment might be therapeutically useful as an antifibrotic strategy in a variety of liver diseases.

FXR promotes endothelial cell motility through coordinated regulation of FAK and MMP-9

OBJECTIVE

Farnesoid X Receptor (FXR) mediates important signaling functions of bile acids in diverse cell types including those residing in the vascular wall. Indeed, recent work has identified FXR as a potential regulator of vascular structure and function in part through transcriptional activation of MMP-9. However, the signal transduction pathways linking bile acids to changes in actin cytoskeleton that are responsible for bile acid-induced vascular cell migration remain unexplored.

METHODS AND RESULTS

The FXR agonist and prototypical bile acid, chenodeoxycholic acid (CDCA), significantly increased endothelial cell (EC) motility, as analyzed by time lapse video microscopy, and tube formation, an in vitro correlate for angiogenesis. Increased cell motility was associated with prominent increases in focal adhesion (FA) plaques and was inhibited by FXR or MMP-9 siRNA, indicating a FXR-MMP-9-dependency of this signaling pathway. Mechanistically, incubation of cells with CDCA was associated with phosphorylation of a key FA protein, Focal Adhesion Kinase (FAK) at Y397 but not at Y576/577, or Y925. Studies using a site-specific phosphorylation mutant (phosphodeficient) of FAK revealed that FAK phosphorylation at tyrosine residue -397 was required for CDCA induced activation of the downstream FA assembly protein, paxillin. Lastly, siRNA-based silencing of FAK as well as phosphodeficient FAK mutant inhibited CDCA induced upregulation of MMP-9, cell motility, and vascular tube formation.

CONCLUSIONS

Thus, this study demonstrates a pivotal role for FAK in the process of FXR-induced and MMP-9-dependent EC motility and vascular tube formation.

Enhanced serum concentrations of transforming growth factor-beta1 in simple fatty liver: is it really benign?

Background

Inside the spectrum of non-alcoholic fatty liver disease, simple fatty liver is generally thought of as being "non progressive", differently from non-alcoholic steatohepatitis, which increases in severity due to the presence of apoptosis/inflammation and fibrosis. The "benignity" of fatty liver is widely accepted but conceptually difficult to maintain because the mechanisms underlying this entity are the same ones that determine the more severe form.

Findings provide evidence that iron overload is associated with increased liver damage and collagen deposition. Transforming growth factor-beta1 released by hepatic stellate cells during chronic liver injury plays a critical role in liver apoptosis and fibrogenesis.

Objective

To verify whether both the forms of non-alcoholic fatty liver disease were really dissimilar, evaluating the serum profile of two key parameters, indexes of severity.

Methods

A total of 123 patients (57 females) participated, forming three groups: forty five patients with fatty liver, 42 patients with non-alcoholic steatohepatitis and 36 with chronic hepatitis C. All had a biopsy-proven diagnosis.

Measurements

Serum concentrations of transforming growth factor-beta1 and ferritin.

Results

High concentrations of transforming growth factor-beta1 were noticed in patients suffering from both fatty liver and non-alcoholic steatohepatitis, 129.1 (45.4) versus 116.8 (42.2) ng/mL, P = 0.2; they were significantly superior to those of chronic hepatitis C patients 87.5 (39.5) ng/mL, P < 0.001. Ferritin levels were on average above normal values and similar in the three groups (P = 0.9), also when adjusted for gender (P = 0.5) and age (P = 0.3).

Conclusion

No difference between serum concentrations of transforming growth factor-beta1 and ferritin in fatty liver and non-alcoholic steatohepatitis suggests that these forms share more common aspects, regarding their progression, than previously thought.

Nitric oxide regulates tumor cell cross-talk with stromal cells in the tumor microenvironment of the liver

Tumor progression is regulated through paracrine interactions between tumor cells and stromal cells in the microenvironment, including endothelial cells and myofibroblasts. Nitric oxide (NO) is a key molecule in the regulation of tumor-microenvironment interactions, although its precise role is incompletely defined. By using complementary in vitro and in vivo approaches, we studied the effect of endothelial NO synthase (eNOS)-derived NO on liver tumor growth and metastasis in relation to adjacent stromal myofibroblasts and matrix because liver tumors maintain a rich, vascular stromal network enriched with phenotypically heterogeneous myofibroblasts. Mice with an eNOS deficiency developed liver tumors more frequently in response to carcinogens compared with control animals. In a surgical model of pancreatic cancer liver metastasis, eNOS overexpression in the tumor microenvironment attenuated both the number and size of tumor implants. NO promoted anoikis of tumor cells in vitro and limited their invasive capacity. Because tumor cell anoikis and invasion are both regulated by myofibroblast-derived matrix, we explored the effect of NO on tumor cell protease expression. Both microarray and Western blot analysis revealed eNOS-dependent down-regulation of the matrix protease cathepsin B within tumor cells, and silencing of cathepsin B attenuated tumor cell invasive capacity in a similar manner to that observed with eNOS overexpression. Thus, a NO gradient within the tumor microenvironment influences tumor progression through orchestrated molecular interactions between tumor cells and stroma.

The therapeutic potential of bone marrow-derived mesenchymal stem cells on hepatic cirrhosis

Hepatic cirrhosis is the end-stage of chronic liver diseases. The majority of patients with hepatic cirrhosis die from life-threatening complications occurring at their earlier ages. Liver transplantation has been the most effective treatment for these patients. Since liver transplantation is critically limited by the shortage of available donor livers, searching for an effective alternative therapy has attracted great interest in preclinical studies. The transplantation of autologous bone marrow-derived mesenchymal stem cells holds great potential for treating hepatic cirrhosis. Mesenchymal stem cells can differentiate to hepatocytes, stimulate the regeneration of endogenous parenchymal cells, and enhance fibrous matrix degradation. Experimental and clinical studies have shown promising beneficial effects. This review is intended to translate the bench study results to the patients' bedside. The potential interventions of mesenchymal stem cells on cirrhosis are illustrated in terms of the cellular and molecular mechanisms of hepatic fibrogenesis.

The prevention of endothelial dysfunction through endothelial cell apoptosis inhibition in a hypercholesterolemic rabbit model: the effect of L-arginine supplementation

BACKGROUND

The impact of L-arginine on atherogenesis and its ability to prevent endothelial dysfunction have been studied extensively during the past years. L-arginine is a substance for nitric oxide synthesis which involves in apoptosis. Hypercholesterolemia promotes endothelial dysfunction, and it is hypothesized that L-arginine prevents endothelial dysfunction through endothelial cells apoptosis inhibition. To test this hypothesis, thirty rabbits were assigned into two groups. The control group received 1% cholesterol diet for 4 weeks, and the L-arginine group received same diets plus 3% L-arginine in drinking water.

RESULTS

No significant differences were observed in cholesterol level between two groups, but the nitrite concentration in L-arginine group was significantly higher than other group (control group: 11.8 +/- 1; L-arginine group: 14.7 +/- 0.5 micromol/l); (p < 0.05). The aorta score of fatty streak in control group was 0.875 +/- 0.35, but no fatty streak lesion was detected in L-arginine group (p < 0.05). The number of intimal apoptotic cells/500 cells of aorta in two groups of experiment were statistically different (control group: 39.3 +/- 7.6; L-arginine group: 21.5 +/- 5.3) (p < 0.05).

CONCLUSION

The inhibition of endothelial cells apoptosis by L-arginine restores endothelial function in a model of hypercholesterolemia.