Hepatic expression of c-Myb in chronic human liver disease

A novel antifibrotic strategy utilizing conditioned media obtained from miR-150-transfected adipose-derived stem cells: validation of an animal model of liver fibrosis

The limitations of stem cells have led researchers to investigate the secretome, which is the secretory materials in stem cells, since the principal mechanism of action of stem cells is mediated by the secretome. In this study, we determined the antifibrotic potential of the secretome released from miR-150-transfected adipose-derived stromal cells (ASCs). The secretome released from ASCs that were transfected with antifibrotic miR-150 was obtained (referred to as the miR-150 secretome). To validate the antifibrotic effects of the miR-150 secretome, we generated in vitro and in vivo models of liver fibrosis by treating human hepatic stellate cells (LX2 cells) with thioacetamide (TAA) and subcutaneous injection of TAA into mice, respectively. In the in vitro model, more significant reductions in the expression of fibrosis-related markers, such as TGFβ, Col1A1, and α-SMA, were observed by using the miR-150 secretome than the control secretome, specifically in TAA-treated LX2 cells. In the in vivo model, infusion of the miR-150 secretome into mice with liver fibrosis abrogated the increase in serum levels of systemic inflammatory cytokines, such as IL-6 and TNF-α, and induced increased expression of antifibrotic, proliferation, and antioxidant activity markers in the liver. Our in vitro and in vivo experiments indicate that the miR-150 secretome is superior to the naive secretome in terms of ameliorating liver fibrosis, minimizing systemic inflammatory responses, and promoting antioxidant enzyme expression. Therefore, we conclude that miR-150 transfection into ASCs has the potential to induce the release of secretory materials with enhanced antifibrotic, proliferative, and antioxidant properties.

A mixture of molecules produced by genetically modified stem cells could help repair the damage associated with liver fibrosis. Fat-derived adipose stem cells (ASCs) secrete proteins and nucleic acids that can facilitate tissue regeneration, but the natural mixture of molecules secreted (the ‘secretome’) is insufficient to reverse advanced fibrosis. Researchers led by Say-June Kim of the Catholic University of Korea, Seoul, South Korea, have boosted the potency of this cell-derived treatment by engineering ASCs to produce an RNA called miR-150. This RNA inhibits biological processes that drive fibrosis. Experiments in cultured cells and a mouse model of fibrosis confirmed that miR-150 consistently improved the ASC secretome’s capacity to control liver fibrosis and minimize systemic inflammatory responses. This approach could thus offer a safe strategy for promoting tissue regeneration and preventing liver failure.

The effect of the hepatitis C virus (HCV) NS3 protein on the expression of miR-150, miR-199a, miR-335, miR-194 and miR-27a

Hepatitis C virus (HCV) infection is considered one of the most important causes of chronic liver diseases. Many reports have shown that the proteins of the HCV via interactions with gene expression regulatory networks such as cellular pathways and microRNAs can contribute to the development of chronic liver diseases. The present study aimed to investigate the effects of the HCV NS3 protein on the expression of miR-150 miR-199a, miR-335, miR-194, miR-27a in a cell culture model. Plasmids expressing the full length of the HCV NS3 protein were transfected into the LX-2 cell line, while at the same time a plasmid expressing empty GFP (green fluorescent protein) was used as a negative control group. Subsequently, total RNA was extracted and real-time PCR was performed to measure microRNA expression levels. Additionally, the trypan blue exclusion test was performed to examine the effect of the expressing NS3 protein plasmid on cellular viability. The analysis of microRNA gene expression in LX-2 cells indicated that the NS3 protein, which is endogenous to HCV, can significantly upregulate the expression of miR-27a and downregulate the expression of miR-335 and miR-150 in comparison with the control plasmid expressing GFP and normal cells (p < 0.01). These results suggest that the HCV NS3 protein may play a role in the pathogenesis of chronic hepatic diseases such as liver fibrosis via interaction with cellular microRNAs and modulation of microRNA gene expressions.

Endoplasmic reticulum stress enhances fibrosis through IRE1α-mediated degradation of miR-150 and XBP-1 splicing

ER stress results in activation of the unfolded protein response and has been implicated in the development of fibrotic diseases. In this study, we show that inhibition of the ER stress-induced IRE1α signaling pathway, using the inhibitor 4μ8C, blocks TGFβ-induced activation of myofibroblasts in vitro, reduces liver and skin fibrosis in vivo, and reverts the fibrotic phenotype of activated myofibroblasts isolated from patients with systemic sclerosis. By using IRE1α(-/-) fibroblasts and expression of IRE1α-mutant proteins lacking endoribonuclease activity, we confirmed that IRE1α plays an important role during myofibroblast activation. IRE1α was shown to cleave miR-150 and thereby to release the suppressive effect that miR-150 exerted on αSMA expression through c-Myb. Inhibition of IRE1α was also demonstrated to block ER expansion through an XBP-1-dependent pathway. Taken together, our results suggest that ER stress could be an important and conserved mechanism in the pathogenesis of fibrosis and that components of the ER stress pathway may be therapeutically relevant for treating patients with fibrotic diseases.

S100A4 promotes liver fibrosis via activation of hepatic stellate cells

BACKGROUND & AIMS

S100A4 has been linked to the fibrosis of several organs due to its role as a fibroblast-specific marker. However, the role of S100A4 itself in the development of fibrosis has not been much investigated. Here, we determined whether S100A4 regulates liver fibrogenesis and examined its mechanism by focusing on the activation of hepatic stellate cells (HSCs).

METHODS

S100A4 deficient mice were used to determine the role of S100A4 in liver fibrogenesis. The effect of S100A4 on HSC activation was estimated by using primary mouse HSCs and the human HSC cell line LX-2. Serum levels of S100A4 in cirrhotic patients were determined by ELISA.

RESULTS

S100A4 was found to be secreted by a subpopulation of macrophages and to promote the development of liver fibrosis. It accumulated in the liver during the progression of liver fibrosis and activated HSCs in mice. In vitro studies demonstrated that S100A4 induced the overexpression of alpha-smooth muscle actin through c-Myb in HSCs. Both, the selective depletion of S100A4-expressing cells and knockdown of S100A4 in the liver by RNA interference, resulted in a reduction of liver fibrosis following injury. Importantly, increased S100A4 levels in both the liver tissue and serum correlated positively with liver fibrosis in humans.

CONCLUSIONS

S100A4 promotes liver fibrosis by activating HSCs, which may represent a potential target for anti-fibrotic therapies.

Activation of hepatic stellate cells is suppressed by microRNA-150

microRNAs (miRNAs) have recently been reported to be involved in the progression of liver fibrosis. It has previously been shown that miR-150 can inhibit the activation of hepatic stellate cells (HSCs) via the inhibition of C-myb expression. However, the reduced C-myb expression is not responsible for all the effects of miR-150, there may be other molecular mechanisms for the suppression of HSCs by miR-150. In this study, gene array analysis was performed to analyze the miRNAs that were differentially expressed between LX-2 cells induced by transforming growth factor-β1 (TGF-β1) and the control. Our results indicated that the expression of miR-150 was significantly reduced during liver fibrosis. Of note, the reduction of miR-150 induced by TGF-β1 was in a dose- and time-dependent manner. In addition, miR-150 overexpression in LX-2 cells resulted in the inhibition of cell proliferation and the reduction of extracellular matrix proteins and α-smooth muscle actin (α-SMA). However, there was no significant change in the rate of apoptosis in cells transfected with miR-150 mimics compared with the control. Sp1, a mediator of α-1 (I) collagen (Col1A1) expression, and Col4A4 were found to be the targets for miR-150. Also, miR-150 mimics were found to decrease the expression of Sp1 and Col4A4. Smad2 and p-Smad2, the upstream mediators of Sp1, were not affected by miR-150. The same result was also seen in the levels of Smad3 and p-Smad3. Collectively, we conclude that miR-150 can reduce type Ⅰ and IV collagen by directly binding to Sp1 and Col4A4 without the involvement of upstream of the TGF-β/Smad pathway.

A cis-acting regulatory variation of the estrogen receptor α (ESR1) gene is associated with hepatitis B virus-related liver cirrhosis

The hepatic fibrogenesis and sexual dimorphism of hepatitis B virus-related liver cirrhosis (HBV-LC) are related to estrogen and its receptors. Abnormal expression of estrogen receptor α (ESR1) is implicated in the development of cirrhosis in both animal models and humans. Here, we examine whether the ESR1 polymorphisms are related to HBV-LC risk among chronic HBV carriers, and we investigate the functional significance of positively associated polymorphisms. A total of 2,404 unrelated Chinese HBV carriers were recruited to conduct the two-stage designed case-control study. Two ESR1 haplotype tagging polymorphisms, c.30T>C (rs2077647) and c.453-397T>C (rs2234693), were genotyped in 1,285 patients with HBV-LC and in 1,119 asymptomatic HBV carriers. We observed a significantly increased susceptibility to HBV-LC associated with the c.30C allele (P = 4.2 × 10(-8) ), c.453-397C allele (P = 2.0 × 10(-8) ), and [c.30C; c.453-397C] haplotype (Dominant model, P = 8.85 × 10(-10) , odds ratio = 1.50, 95% CI 1.32∼1.71) compared with the T alleles and (c.30T; c.453-397T) haplotype of c.30T>C and c.453-397T>C polymorphisms, respectively. Functional analyses were conducted to verify the biological functions of the associated genetic variations and showed that the c.453-397T>C polymorphism is a novel c.453-397C allele-specific and c-myb-dependent enhancer-like cis-acting regulatory variation and could be part of the genetic variations underlying the susceptibility of individuals to HBV-LC.

Liver fibrosis causes downregulation of miRNA-150 and miRNA-194 in hepatic stellate cells, and their overexpression causes decreased stellate cell activation

Activation of hepatic stellate cells (HSC) results in their proliferation and in the secretion of extracellular matrix (ECM) proteins, which leads to hepatic fibrosis. microRNAs (miRNAs) have been shown to regulate various cell functions, such as proliferation, differentiation, and apoptosis. Hence, we have analyzed the miRNAs that were differentially expressed in HSC isolated from sham-operated and bile duct-ligated rats. Expression of two miRNAs, miRNA-150 and miRNA-194, was reduced in HSC isolated from fibrotic rats compared with sham-operated animals. These two miRNAs were overexpressed in LX-2 cells, and their ability to inhibit cell proliferation, the expression of smooth muscle alpha-actin (SMA), a marker for activation, and collagen type I, a marker for ECM secretion, was determined. Overexpression of these two miRNAs resulted in a significant inhibition of proliferation (P < 0.05) and reduced SMA and collagen I levels compared with either untreated cells or nonspecific miRNA-expressing cells. Next, the protein targets of these two miRNAs were found using bioinformatics approaches. C-myb was found to be a target for miRNA-150, and rac 1 was found to be one of the targets for miRNA-194. Therefore, we studied the expression of these two proteins by overexpressing these two miRNAs in LX-2 cells and found that overexpression of miRNA-150 and miRNA-194 resulted in a significant inhibition of c-myb and rac 1 expression, respectively. We conclude that both miRNA-150 and miRNA-194 inhibit HSC activation and ECM production, at least in part, via inhibition of c-myb and rac 1 expression.

Transcriptional regulation of hepatic stellate cells

Hepatic stellate cell (HSC) activation is a process of cellular transdifferentiation in which, upon liver injury, the quiescent vitamin A storing perisinusoidal HSC is converted into a wound-healing myofibroblast and acquires potent pro-inflammatory and pro-fibrogenic activities. This remarkable phenotypic transformation is underpinned by changes in the expression of a vast number of genes. In this review we survey current knowledge of the transcription factors that either control HSC activation or which regulate specific fibrogenic functions of the activated HSC such as collagen expression, proliferation and resistance to apoptosis.

Effects of c-myb antisense RNA on TGF-β1 and α1-I collagen expression in cultured hepatic stellate cells

AIM: To investigate the effects of c-myb antisense RNA on cell proliferation and the expression of c-myb, TGF-β1 and α1-I collagen in cultured hepatic stellate cells (HSC) from rats.

METHODS: Recombinant retroviral vector of c-myb antisense gene (pDOR-myb) was constructed, and then transfected into retroviral package cell line PA317 by means of DOTAP. The pseudoviruses produced from the resistant PA317 cells were selected with G418 to infect HSCs isolated from rat livers. The cell proliferation was measured by 3-[4, 5-Dimethylthiazolzyl]-2, 5-diphenyl tetrazo-dium bromide (MTT) method.The expression of c-myb, α1-I collagen and TGF-β1 mRNA, and c-myb protein in HSCs was detected with semi-quantitive reverse transeription-polymerase chain reaction (RT-PCR) and Western-blot respectively.

RESULTS: HSCs from rats were isolated successfully with the viability > 98%. In the pDOR-myb infected HSCs, the c-myb protein expression, cell proliferation,and α1-I collagen and TGF-β1 mRNA expression were repressed significantly compared with their corresponding control groups (P < 0.01).

CONCLUSION: c-myb plays a key role in activation and proliferation of HSC. c-myb antisense RNA can inhibit cell proliferation, α1-I collagen and TGF-β1 mRNA expression, suggesting that inhibition of c-myb gene expression might be a potential way for the treatment of liver fibrosis.

Effects of PD98059 on proliferation of rat cultured hepatic stellate cells stimulated by acetaldehyde

AIM

To study the effects of PD98059, the specific blocking agent of MEK1, on the proliferation of hepatic stellate cells and expression of Proliferating Cell Nuclear Antigen in rat hepatic stellate cells (HSC).

METHODS

HSC stimulated by acetaldehyde were cultured. The cell growth was evaluated by MTT colorimetric assay. Proliferating cell nuclear antigen (PCNA) was examined by immunocytochemical staining.

RESULTS

PD98059 of 20 μmol/L had an inhibitory effect on proliferation of HSC (P<0.05, 0.109±0.020 vs 0.146±0.030), which was more obvious when cells exposed to PD98059 at 50 and 100 μmol /L (P<0.05, 0.081±0.010, 0.056±0.020 vs 0.146±0.030), and the expression of PCNA also showed a descending tendency with the increase of PD98059 concentration (P<0.05, 0.62±0.09, 0.47±0.04, 0.34±0.04 vs 0.740.05)

CONCLUSION

PD98059 inhibits proliferation of HSC and expression of PCNA, which is correlated with the decreased activity of PCNA.

The role of c-Myb and Sp1 in the up-regulation of methionine adenosyltransferase 2A gene expression in human hepatocellular carcinoma

Liver-specific and non-liver-specific methionine adenosyltransferase (MAT) are products of two genes, MAT1A and MAT2A, respectively, that catalyze the formation of S-adenosylmethionine. We showed a switch from MAT1A to MAT2A expression at the transcriptional level in human hepatocellular carcinoma (HCC) that facilitates cancer cell growth. The purpose of the present study was to better understand the molecular mechanism of increased MAT2A expression in HCC. In vitro DNase I footprinting analysis revealed two protected sites (-354 to -312 and -73 to -28) using nuclear proteins from HCC and HepG2 cells, but not normal liver. These sites are also protected in HepG2 cells on in vivo DNase I footprinting analysis. These protected sites contain consensus binding sites for c-Myb and Sp1. In HCC, the mRNA levels of c-myb and Sp1 and binding to their respective sites increased. Mutation of the c-Myb or Sp1 site reduced MAT2A promoter activity by 67% and 50%, respectively. The importance of these cis-acting elements and trans-activating factors was confirmed using heterologous promoter and expression vectors. Increased expression of c-Myb and Sp1 and binding to the MAT2A promoter contribute to transcriptional up-regulation of MAT2A in HCC.-Yang, H., Huang, Z.-Z., Wang, J., Lu, S. C. The role of c-Myb and Sp1 in the up-regulation of methionine adenosyltransferase 2A gene expression in human hepatocellular carcinoma.