TAF and TDF attenuate liver fibrosis through NS5ATP9, TGFß1/Smad3, and NF-κB/NLRP3 inflammasome signaling pathways.

BACKGROUND: This study aimed to investigate the roles and mechanisms of tenofovir alafenamide fumarate (TAF)/tenofovir disoproxil fumarate (TDF) in treating liver fibrosis. METHODS: The effects of TAF/TDF on carbon tetrachloride (CCl4)-induced liver fibrosis in C57BL/6 wild-type or nonstructural protein 5A transactivated protein 9 (NS5ATP9) knockout mice were studied. The differentiation, activation, and proliferation of LX-2 cells after TAF/TDF treatment were tested in vitro. The expression of NS5ATP9 and activities of transforming growth factor-ß1 (TGFß1)/Sekelsky mothers against decapentaplegic homolog 3 (Smad3) and NF-κB/NOD-like receptor pyrin domain containing 3 (NLRP3) inflammasome signaling pathways were detected in TAF/TDF-treated mice and LX-2 cells. The genes related to extracellular matrix accumulation were detected in vivo and in vitro after NS5ATP9 silencing or knockout. RESULTS: TAF/TDF significantly inhibited CCl4-induced liver fibrosis in mice, and regulated the differentiation, activation, and proliferation of hepatic stellate cells (HSCs). Furthermore, TAF/TDF suppressed the activities of TGFß1/Smad3 and NF-κB/NLRP3 inflammasome signaling pathways in vivo and in vitro. NS5ATP9 inhibited liver fibrosis through TGFß1/Smad3 and NF-κB signaling pathways. TAF/TDF upregulated the expression of NS5ATP9 in vivo and in vitro. Finally, TAF/TDF could only show marginal therapeutic effects when NS5ATP9 was silenced and knocked out in vivo and in vitro. CONCLUSIONS: TAF/TDF prevented progression and promoted reversion of liver fibrosis through assembling TGFß1/Smad3 and NF-κB/NLRP3 inflammasome signaling pathways via upregulating the expression of NS5ATP9. TAF/TDF also regulated the differentiation, activation, and proliferation of HSCs. The findings provided strong evidence for the role of TAF/TDF as a new promising therapeutic strategy in liver fibrosis.

Hepatitis C virus nonstructural 5A protein inhibits the starvation­induced apoptosis of hepatoblastoma cells by increasing Beclin 1 expression.

Hepatitis C virus (HCV) nonstructural protein 5A (NS5A) modulates cellular apoptosis, which is involved in the occurrence and development of liver cancer. The mechanisms of apoptosis inhibition by NS5A in liver cancer cells remains unclear. Beclin 1, which functions upstream of autophagosome formation, is upregulated by NS5A. Autophagy, an evolutionarily conserved catabolic process, has a crucial role in tumor initiation and progression. Autophagy was blocked by inhibitors 3­methyladenine and chloroquine, or via knockdown of Beclin 1. Flow cytometric analysis and western blotting were used to detect apoptosis. It was found that inhibition of autophagy attenuated the NS5A­mediated apoptosis inhibition of HepG2 cells. Furthermore, it was confirmed that Beclin 1 expression by NS5A was involved in the negative regulation of starvation­induced liver cancer apoptosis, which was accompanied by reduced p53 and apoptosis regulator Bax expression, as well as decreased caspase­3/-7 activation. Therefore, inhibition of autophagy may be promising therapeutic strategy in the treatment of HCV­associated liver cancer.

miR-185 Inhibits Fibrogenic Activation of Hepatic Stellate Cells and Prevents Liver Fibrosis.

Recent studies have shown the effect of microRNAs on HSC activation and transformation, which is essential for the pathogenesis of liver fibrosis. In our study, we explored the role of miR-185 in liver fibrosis. Plasma miR-185 was detected in hepatitis B virus-related liver fibrosis patients (S2/3, n = 10) by Illumina HiSeq sequencing, and healthy volunteers were selected (n = 8) as the control group. We found that the plasma miR-185 level in fibrosis patients was significantly downregulated. CCl4-induced fibrosis tissues in mouse livers and TGF-ß1-activated HSCs also presented downregulated miR-185 concomitant with an increased expression of RHEB and RICTOR. To explore the correlations, LX-2 cells were transiently transfected with miR-185 mimics. The expression levels of α-SMA, collagen I, and collagen III were decreased as well as RHEB and RICTOR. Inhibition of endogenous miR-185 increased fibrogenic activity. Furthermore, dual-luciferase reporter assays indicated that miR-185 inhibited the expression of RHEB and RICTOR by directly targeting their 3' UTRs. Moreover, silencing RHEB and RICTOR suppressed α-SMA and collagen expression levels. In conclusion, miR-185 prevents liver fibrogenesis by inhibiting HSC activation via inhibition of RHEB and RICTOR. These results provide new insights into the mechanisms behind the anti-fibrotic effect of miR-185.

Role of IL-6-mediated expression of NS5ATP9 in autophagy of liver cancer cells.

This study aimed to investigate the relationship between interleukin-6 (IL-6) and NS5ATP9 in autophagy of liver cancer cells. Autophagy is one of the important regulators of the replication of hepatitis C virus and the survival of tumors. IL-6 is a multifunctional cytokine that plays an important role in autophagy and development of many kinds of tumors. However, the role of IL-6 in autophagy has not been fully explored. A previous study had shown that a novel gene, NS5ATP9, could modulate autophagy. The present study demonstrated that human IL-6 recombinant protein induced autophagy of HepG2 cells. Conversely, autophagy decreased after IL-6 was silenced or neutralized with monoclonal antibody against human IL-6. In addition, NS5ATP9 was upregulated by IL-6 via nuclear factor-kappaB activation, as detected by Western blot. Further studies indicated that the induction of autophagy by IL-6 could be attenuated by silencing NS5ATP9. Interestingly, the expression of NS5ATP9, in turn, resulted in the upregulation of IL-6. In conclusion, IL-6 could induce autophagy by expressing NS5ATP9, while NS5ATP9 upregulated IL-6 levels in turn, which further induced autophagy.

HCBP6 upregulates human SREBP1c expression by binding to C/EBPß-binding site in the SREBP1c promoter.

Sterol regulatory element-binding protein-1c (SREBP1c) plays an important role in triglyceride (TG) homeostasis. Although our previous study showed that hepatitis C virus core-binding protein 6 (HCBP6) regulates SREBP1c expression to maintain intracellular TG homeostasis, the mechanism underlying this regulation is unclear. In the present study, we found that HCBP6 increased intracellular TG levels by upregulating SREBP1c expression. HCBP6 increased SREBP1c transcription by directly binding to the SREBP1c promoter (at the -139- to +359-bp region). Moreover, we observed that HCBP6 interacted with C/EBPß-binding site in the SREBP1c promoter both in vitro and in vivo. These results indicate that HCBP6 upregulates human SREBP1c expression by binding to the C/EBPß-binding site in the SREBP1c promoter. [BMB Reports 2018; 51(1): 33-38].

Prevalence of NS5B resistance-associated variants in treatment-naïve Asian patients with chronic hepatitis C.

There is little information on the association between baseline non-structural protein (NS) 5b resistance-associated variants (RAVs) and treatment failure in hepatitis C patients. This study examined the frequencies of natural hepatitis C virus (HCV) NS5B resistance-associated variants (RAVs) in an Asian cohort. Samples from Asian HCV patients enrolled between October 2009 and September 2014 were analyzed for NS5B RAVs within the region from amino acid 230 to 371. Serum samples were tested by PCR genotyping, with sequence alignment performed using the neighbor-joining method. NS5B was detected by Sanger sequencing followed by Geno2pheno analysis. NS5B RAVs were detected in 80.52% (1199/1489) of patients; 68.4% (1019/1489) and 79.7% (1186/1489) were associated with resistance to sofosbuvir (SOF) and dasabuvir (DSV), respectively. These RAVs were present in 95% (1004/1058) of genotype 1b patients. When genotypes 1b and 2a were compared, SOF-associated RAVs were detected at a higher frequency in genotype 1b (94.8% [1004/1058] vs. 2.9% [9/309]; χ2 = 1054.433, P < 0.001), C316H/N was more common in genotype 1b (94.7% [1002/1058] vs. 0% [0/309]; χ2 = 1096.014, P < 0.001), M289F/L/I/W/V had a higher frequency in genotype 2a (0.7% [7/309] vs. 2.3% [7/1058]; χ2 = 4.589, P = 0.032), DSV-associated RAVs were most often found in genotype 1b (95.0% [1005/1058] vs. 40.1% 124/309]; χ2 = 500.577, P < 0.001), and frequency of C316Y/H/N/W was higher in genotype 1b (94.7% [1002/1058] vs. 0% [0/309]; χ2 = 1096.014, P < 0.001). In conclusion, baseline SOF and DSV RAVs are common in Asian HCV patients and predominantly occur in genotype 1b.

MicroRNA-185 induces potent autophagy via AKT signaling in hepatocellular carcinoma.

Studies have demonstrated that microRNA 185 may be a promising therapeutic target in liver cancer. However, its role in hepatocellular carcinoma is largely unknown. In this study, the proliferation of human HepG2 cells was inhibited by transfection of microRNA 185 mimics. Cell-cycle analysis revealed arrest at the G0/G1 phase. Transfection of HepG2 cells with microRNA 185 mimics significantly induced apoptosis. These data confirmed microRNA 185 as a potent cancer suppressor. We demonstrated that microRNA 185 was a compelling inducer of autophagy, for the first time. When cell autophagy was inhibited by chloroquine or 3-methyladenine, microRNA 185 induced more cell apoptosis. MicroRNA 185 acted as a cancer suppressor by regulating AKT1 expression and phosphorylation. Dual-luciferase reporter assays indicated that microRNA 185 suppressed the expression of target genes including RHEB, RICTOR, and AKT1 by directly interacting with their 3'-untranslated regions. Binding site mutations eliminated microRNA 185 responsiveness. Our findings demonstrate a new role of microRNA 185 as a key regulator of hepatocellular carcinoma via autophagy by dysregulation of AKT1 pathway.

NS5ATP13 Promotes Liver Fibrogenesis Via Activation of Hepatic Stellate Cells.

Liver fibrosis is a reversible wound-healing response to any etiology of chronic hepatic injuries. Activation of hepatic stellate cells (HSCs) is the key event in liver fibrogenesis. Generally, persistent activation and proliferation of HSCs results in liver fibrosis progression, while primary mechanisms of liver fibrosis resolution are apoptosis and reversion to a quiescent phenotype of activated HSCs. NS5ATP13 (HCV NS5A-transactivated protein 13) is involved in nucleologenesis and tumorigenesis, but its role in liver fibrosis and HSC activation remains unclear. This study found that NS5ATP13 was upregulated in both fibrotic liver tissues and activated human HSCs induced by TGF-ß1. Moreover, NS5ATP13 enhanced extracellular matrix (ECM) production and HSC activation, with or without TGF-ß1 treatment, likely involving the TGF-ß1/Smad3 signaling pathway. Additionally, NS5ATP13 boosted HSC proliferation by inhibiting cell apoptosis. Furthermore, HCV NS5A promoted the profibrogenic effect of NS5ATP13 partly through TGF-ß1 and NF-κB p65 (RelA) upregulation. Meanwhile, NS5ATP13 was required for the pro-fibrogenic effect of NF-κB. Moreover, NS5ATP13 and NF-κB phosphorylation as well as HSC activation were reduced by CX-4945, a CK2 specific inhibitor. These findings indicated that NS5ATP13 acts as a profibrogenic factor, providing a potential target for antifibrotic therapies. J. Cell. Biochem. 118: 2463-2473, 2017. © 2017 Wiley Periodicals, Inc.

NS5ABP37 inhibits liver cancer by impeding lipogenesis and cholesterogenesis.

The molecular mechanism underlying non-alcoholic fatty liver disease progression to hepatocellular carcinoma (HCC) remains unknown. In this study, immunohistochemistry staining results showed that NS5ABP37 protein, which is in a state of lower expression in tumor tissues, decreased with increasing degree of HCC malignancy. Two cell models, HepG2 and L02, were used to analyze the mechanism between NS5ABP37 and HCC. In agreement, NS5ABP37 protein overexpression significantly suppressed cell proliferation, caused G1 /S cell cycle arrest, and induced apoptosis by increasing caspase-3/7 activity and cleaved caspase-3 levels. In addition, NS5ABP37 overexpression resulted in decreased intracellular triglyceride and total cholesterol contents, with level reduction in sterol regulatory element-binding proteins (SREBPs) and downstream effectors. Furthermore, NS5ABP37 overexpression decreased SREBP1c and SREBP2 levels by reducing their respective promoters. Finally, reactive oxygen species levels and endoplasmic reticulum stress were both induced by NS5ABP37 overexpression. These findings together indicate that NS5ABP37 inhibits cancer cell proliferation and promotes apoptosis, by altering SREBP-dependent lipogenesis and cholesterogenesis in HepG2 and L02 cells and inducing oxidative stress and endoplasmic reticulum stress.

NS5ATP6 modulates intracellular triglyceride content through FGF21 and independently of SIRT1 and SREBP1.

The prevalence of nonalcoholic fatty liver disease (NAFLD) is rising strikingly in Western countries and China. The molecular biological mechanism of NAFLD remains unclear, with no effective therapies developed so far. Fibroblast growth factor 21 (FGF21) is a recently discovered hormone, with safe lipid lowering effects. FGF21 analogs are being developed for clinical application. Here we demonstrated that a novel gene, NS5ATP6, modulated intracellular triglyceride (TG) content independently of sirtuin1 (SIRT1) and sterol regulatory element binding protein 1 (SREBP1) in HepG2 cells. Interestingly, NS5ATP6 regulated FGF21 expression both at the mRNA and protein levels. The modulatory effects of NS5ATP6 on intracellular TG content depended upon FGF21. Further studies revealed that NS5ATP6 decreased the promoter activity of FGF21. In addition, NS5ATP6 regulated the expression of miR-577, which directly targeted and regulated FGF21. Therefore, miR-577 might be involved in NS5ATP6 regulation of FGF21 at the post-transcriptional level. In conclusion, NS5ATP6 regulates the intracellular TG level via FGF21, and independently of SIRT1 and SREBP1.

Regulation of HepG2 cell apoptosis by hepatitis C virus (HCV) core protein via the sirt1-p53-bax pathway.

Hepatitis C virus (HCV) core protein stimulates many signaling pathways related to apoptosis inhibition resulting in hepatocellular carcinoma (HCC). It has been reported that sirt1 is involved in regulating apoptosis; therefore, we investigated the influence of HCV core protein on sirt1 expression and apoptosis in human HepG2 cells. Our study showed that HCV core protein inhibited apoptosis of HepG2 cells as well as caspase-3 expression and activity (P < 0.05). At the same time, sirt1 expression was increased at both the mRNA (P < 0.05) and protein (P < 0.05) levels. Furthermore, apoptosis inhibition was reversed when sirt1 was knocked down (P < 0.05). Our study provides further evidence that the sirt1-p53-Bax signaling pathway plays an important role in regulating the suppression of cell apoptosis induced by HCV core protein.

Hepatitis C virus genotype and subtype distribution in Chinese chronic hepatitis C patients: nationwide spread of HCV genotypes 3 and 6.

BACKGROUND: Hepatitis C virus (HCV) genotype and subtype are related to disease progression and response to antiviral therapy. Current HCV genotype and subtype distribution data, especially for genotypes 3 and 6, are limited in China. Our purpose was to investigate the current HCV genotype and subtype distributions in chronic hepatitis C patients in China. METHODS: Chronic hepatitis C patients (n = 1012) were enrolled, and demographic information and possible transmission risk factors were collected. Serum samples were subjected to reverse-transcription polymerase chain reaction, followed by direct DNA sequencing and phylogenetic analysis of the NS5B and core/E1 regions to determine HCV genotypes/subtypes. The geographical distributions of HCV genotypes/subtypes were analyzed. Demographic information and transmission risk factors were compared between different HCV genotypes/subtypes. RESULTS: Four genotypes and seven subtypes of HCV were detected in 970 patients. Subtypes 1b, 2a, 3a, 6a, 3b, 6n, and 1a were detected at frequencies of 71.96%, 19.90%, 3.20%, 2.16%, 1.96%, 0.41%, and 0.41%, respectively. Genotypes 3 and 6 showed an increasingly wide geographic distribution over time. Patients with subtypes 1b and 2a were older than those with 3a, 3b, 6a, and 6n subtypes (p < 0.05 in all subtypes). More genotype 1 and 2 patients underwent blood transfusion than those with genotype 3 (all p < 0.05). More genotype 3 and 6 patients had a history of intravenous drug use than those with genotypes 1 and 2 (all p < 0.05). CONCLUSIONS: Though subtypes 1b and 2a are still the most prevalent HCV subtypes in China, genotype 3 and 6 HCV infections have already spread nationwide from southern and western China.

MicroRNA-185-5p mediates regulation of SREBP2 expression by hepatitis C virus core protein.

AIM: To investigate the molecular mechanism for regulation of cholesterol metabolism by hepatitis C virus (HCV) core protein in HepG2 cells. METHODS: HCV genotype 1b core protein was cloned and expressed in HepG2 cells. The cholesterol content was determined after transfection. The expression of sterol regulatory element binding protein 2 (SREBP2) and the rate-limiting enzyme in cholesterol synthesis (HMGCR) was measured by quantitative real-time PCR and immunoblotting after transfection. The effects of core protein on the SREBP2 promoter and 3'-untranslated region were analyzed by luciferase assay. We used different target predictive algorithms, microRNA (miRNA) mimics/inhibitors, and site-directed mutation to identify a putative target of a particular miRNA. RESULTS: HCV core protein expression in HepG2 cells increased the total intracellular cholesterol level (4.05 ± 0.17 vs 6.47 ± 0.68, P = 0.001), and this increase corresponded to an increase in SREBP2 and HMGCR mRNA levels (P = 0.009 and 0.037, respectively) and protein expression. The molecular mechanism study revealed that the HCV core protein increased the expression of SREBP2 by enhancing its promoter activity (P = 0.004). In addition, miR-185-5p expression was tightly regulated by the HCV core protein (P = 0.041). Moreover, overexpression of miR-185-5p repressed the SREBP2 mRNA level (P = 0.022) and protein expression. In contrast, inhibition of miR-185-5p caused upregulation of SREBP2 protein expression. miR-185-5p was involved in the regulation of SREBP2 expression by HCV core protein. CONCLUSION: HCV core protein disturbs the cholesterol homeostasis in HepG2 cells via the SREBP2 pathway; miR-185-5p is involved in the regulation of SREBP2 by the core protein.

NS5ATP9 Promotes Beclin 1-Dependent Starvation-Induced Autophagy of Hepatoblastoma Cells.

NS5ATP9, a gene up-regulated by NS5A, plays a crucial oncogenic role in several types of human tumours. However, the underlying mechanisms remain unclear. Autophagy, an evolutionarily conserved catabolic process, maintains cellular homeostasis under stress conditions, such as starvation, and plays a crucial role in tumour initiation and progression. Here, we report that NS5ATP9 mRNA and protein expression was up-regulated in starved HepG2 cells and that the up-regulated NS5ATP9 played a functional role in starvation-induced autophagy. Overexpression or silencing of this gene showed contrasting effects on Beclin 1 and on starvation-induced autophagy. Furthermore, NS5ATP9-mediated autophagy is required for promotion of tumour cell growth, and this effect could be inhibited with 3-methyladenine, chloroquine or by Beclin 1-silencing. Thus, the mechanism for NS5ATP9-promoted autophagy is Beclin 1-dependent in the condition of starvation, and for hepatoblastoma cell growth is also Beclin 1-dependent.