Hepatitis C virus core protein induces dysfunction of liver sinusoidal endothelial cell by down-regulation of silent information regulator 1.

Hepatic fibrosis is a frequent feature of chronic hepatitis C virus (HCV) infection. Some evidence has suggested the potential role of silent information regulator 1 (SIRT1) in organ fibrosis. The aim of this study was to investigate the effect of HCV core protein on expression of SIRT1 of liver sinusoidal endothelial cell (LSEC) and function of LSEC. LSECs were co-cultured with HepG2 cells or HepG2 cells expressing HCV core protein and LSECs cultured alone were used as controls. After co-culture, the activity and expression levels of mRNA and protein of SIRT1 in LSEC were detected by a SIRT1 fluorometric assay kit, real time-PCR (RT-PCR), Western blot, respectively. The levels of adiponectin receptor 2 (AdipoR2), endothelial nitric oxide synthase (eNOS) and vascular endothelial growth factor (VEGF) were measured by Western blot. Cluster of differentiation 31 (CD31), CD14, and von Willebrand factor (vWf) of LSECs was performed by flow cytometry. The level of reactive oxygen species (ROS) was assayed. Malondialdehyde (MDA), superoxide dismutase (SOD), adiponectin, nitric oxide (NO), and endothelin-1 (ET-1) levels in the co-culture supernatant were measured. The co-culture supernatant was then used to cultivate LX-2 cells. The levels of α-smooth muscle actin (ASMA) and transforming growth factor-ß1 (TGF-ß1) protein in LX-2 cells were measured by Western blot. Compared with LSEC co-cultured with HepG2 cells group, in LSEC co-cultured with HepG2-core cells group, the activity and expression level of mRNA and protein of SIRT1 reduced; the level of adiponectin reduced and the expression level of AdipoR2 protein decreased; ROS levels increased; the expression level of eNOS, VEGF protein decreased; and the expression level of CD14 decreased; the expression level of vWf and CD31 increased; NO and SOD levels decreased; whereas ET-1 and MDA levels increased; the levels of ASMA and TGF-ß1 protein in LX-2 cells increased. SIRT1 activator improved the above-mentioned changes. HCV core protein may down-regulate the activity and the expression of SIRT1 of LSEC, then decreasing synthesis of adiponectin and the expression of AdipoR2, thus inducing contraction of LSEC and hepatic sinusoidal capillarization and increasing oxidative stress, ultimately cause hepatic stellate cell (HSC) activation. Treatment with SIRT1 activator restored the function of LSEC and inhibited the activation of HSC.

Bif-1 deficiency impairs lipid homeostasis and causes obesity accompanied by insulin resistance.

Bif-1 is a membrane-curvature inducing protein that is implicated in the regulation of autophagy and tumorigenesis. Here, we report that Bif-1 plays a critical role in regulating lipid catabolism to control the size of lipid droplets and prevent the development of obesity and insulin resistance upon aging or dietary challenge. Our data show that Bif-1 deficiency promotes the expansion of adipose tissue mass without altering food intake or physical activities. While Bif-1 is dispensable for adipose tissue development, its deficiency reduces the basal rate of adipose tissue lipolysis and results in adipocyte hypertrophy upon aging. The importance of Bif-1 in lipid turnover is not limited to adipose tissue since fasting and refeeding-induced lipid droplet clearance is also attenuated by Bif-1 loss in the liver. Interestingly, obesity induced by a high fat-diet or Bif-1 deficiency downregulates the expression of proteins involved in the autophagy-lysosomal pathway, including Atg9a and Lamp1 in the adipose tissue. These findings thus identify Bif-1 as a novel regulator of lipid homeostasis to prevent the pathogenesis of obesity and its associated metabolic complications.

Endocannabinoid system activation contributes to glucose metabolism disorders of hepatocytes and promotes hepatitis C virus replication.

BACKGROUND: Insulin resistance is highly prevalent in patients with chronic hepatitis C (CHC) and to some extent accounts for fibrosis and reducing viral eradication. Activated cannabinoid 1 receptor (CB1R) signaling has been implicated in the development of phenotypes associated with insulin resistance and steatosis. We investigated the role of the endocannabinoid system in glucose metabolism disorders induced by hepatitis C virus (HCV) replication. METHODS: Human hepatic stellate cells (HSC; LX-2 cells) were co-cultured with Huh-7.5 cells or Huh-7.5 cells harboring HCV replicon (replicon cells). Endocannabinoid levels were then measured by liquid chromatography/mass spectrometry. The expression of CB1R and its downstream glucose metabolism genes in hepatocytes were determined by real-time PCR and Western blot. Glucose uptake by hepatocytes and glucose production were measured. Glucose metabolism tests and measurements of HCV RNA levels and nonstructural protein 5A (NS5A) levels were taken after treatment with CB1R agonist arachidonyl-2-chloroethanolamide (ACEA) or antagonist AM251. RESULTS: Compared to the co-culture with Huh-7.5 cells, the level of 2-arachidonoylglycerol (2-AG) and the CB1R mRNA and protein levels increased in the co-culture of LX-2 cells with replicon cells. The activation of CB1R decreased AMP-activated protein kinase (AMPK) phosphorylation, inhibited cell surface expression of glucose transporter 2 (GLUT2), and suppressed cellular glucose uptake; furthermore, it increased cyclic AMP response element-binding protein H (CREBH), then up-regulated phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) genes and down-regulated the glucokinase (GK) gene, thus promoting glucose production. Interferon treatment restored the aforementioned changes. CB1R antagonist improved glucose metabolism disorders by an increase in glucose uptake and a decrease in glucose production, and inhibited HCV replication. CONCLUSIONS: HCV replication may not only increase the 2-AG content, but may also up-regulate the expression of CB1R of hepatocytes, then change the expression profile of glucose metabolism-related genes, thereby causing glucose metabolism disorders of hepatocytes and promoting HCV replication. Treatment with CB1R antagonist improved glucose metabolism disorders and inhibited viral genome replication.

IL-6/STAT3/TFF3 signaling regulates human biliary epithelial cell migration and wound healing in vitro.

Interleukin-6 (IL-6), through activation of the signal transducer and activator of transcription 3 (STAT3) and trefoil factor family 3 (TFF3), has been implicated in the promotion of mouse biliary epithelial cell (BEC) proliferation and migration. However, it is still unclear whether the IL-6/STAT3/TFF3 signaling had similar effects on human BECs. Here, we showed that exposure of human BECs to recombinant IL-6 resulted in STAT3 phosphorylation and increased the expression of TFF3 at both mRNA and protein levels. Moreover, inhibition of STAT3 using RNA interference significantly abrogated IL-6-induced TFF3 expression. In an in-vitro wound healing model, IL-6 facilitated human BEC migration. This promotion of cell migration by IL-6 was blocked when STAT3 was knocked down. Interestingly, the addition of exogenous TFF3 could rescue the cell migration defects caused by STAT3 silencing. In conclusion, our data indicate that STAT3 plays a critical role in IL-6-induced TFF3 expression in human BECs and the IL-6/STAT3/TFF3 signaling is involved in human BEC migration and wound healing.

Reconstitution of secreted frizzled-related protein 1 suppresses tumor growth and lung metastasis in an orthotopic model of hepatocellular carcinoma.

BACKGROUND: Secreted Frizzled-related protein 1 (sFRP1) is frequently silenced in many types of cancer, including hepatocellular carcinoma (HCC), leading to aberrant activation of Wnt signaling and thereby facilitating tumor development. In this study, we aimed to investigate whether restoration of sFRP1 affected HCC growth and metastasis. METHODS: We generated stable cell lines overexpressing sFRP1 in MHCC97-H cells, which naturally do not express detectable sFRP1 messenger RNA (mRNA) and have high metastatic properties. The effects of sFRP1 reexpression on tumor growth and metastasis were assessed in vitro and in vivo. It was also tested whether ß-catenin signaling mediated the function of sFRP1 in tumor progression. RESULTS: Overexpression of sFRP1 substantially diminished the proliferation and invasion potentials of MHCC97-H cells. Furthermore, sFRP1 expression significantly inhibited MHCC97-H xenograft growth and metastasis in vivo, which was accompanied by decreased angiogenesis and increased tumor cell apoptosis. Moreover, sFRP1 overexpression caused less expression of ß-catenin and its downstream effector genes cyclin D1 and matrix metalloproteinase (MMP)-2. CONCLUSION: Together these findings demonstrate that sFRP1 reconstitution suppresses tumor growth, angiogenesis, and metastasis in MHCC97-H xenografts, which may be associated with inactivation of ß-catenin signaling, thus providing a possible therapeutic strategy against HCC.

Use of a cocktail regimen consisting of soluble galectin-1, rapamycin and histone deacetylase inhibitor may effectively prevent type 1 diabetes.

Type 1 diabetes (T1D) is an autoimmune disorder that results in destruction of insulin-releasing beta-cells of the pancreas. During the pathogenesis of T1D, at least two phases of beta-cell death occur: an initiation event wherein macrophage-derived inflammatory cytokines induce beta-cell necrosis and release of beta-cell-specific antigens, and a second, antigen-driven event in which T-cell-mediated immune response is directed against beta-cells. In contrast to macrophages and autoreactive T cells, regulatory T cells play a key role in inducing and maintaining immunological tolerance to self antigens. Therefore, modulation of the immune system may prevent the development of T1D. Herein, we proposed a cocktail regimen consisting of soluble galectin-1, rapamycin and histone deacetylase inhibitor (HDACi) for the treatment of T1D because (a) HDACi has been reported to protect against IL-1beta-mediated loss in beta-cell viability, (b) HDACi and rapamycin have the ability to promote the generation and function of regulatory T cells and thus suppress the cytotoxic T-cell function, and (c) administration of soluble galectin-1 can trigger apoptosis of the beta-cell-reactive T cells. This cocktail regimen may not only block T-cell- and cytokine-mediated autoimmunity but also restore self-tolerance to beta-cell antigens, therefore representing a novel alternative for treatment of T1D.