Increased Smad1 expression and transcriptional activity enhances trans-differentiation of hepatic stellate cells

RUNX1 regulates SMAD1 by transcriptionally activating the expression of USP9X, regulating the activation of hepatic stellate cells and liver fibrosis

Liver fibrosis (LF) is a common pathological process with high morbidity and mortality. Runt-related transcription factor 1 (RUNX1) is a transcription factor that could cause nephropathy and renal fibrosis, but its role in LF is unclear. Therefore, this study aimed to investigate the role RUNX1 in LF. Briefly, hepatic fibrosis was detected by Sirius Red staining. Transcript levels were quantified by qPCR, and proteins were assessed by western blotting or immunofluorescence. Cell viability and cell migration were measured by CCK8 assays and wound healing assays, respectively. The binding of RUNX1 and ubiquitin-specific protease 9X (USP9X) promoter was validated by ChIP assays and luciferase report assays, while the binding of USP9X and SMAD1 was confirmed by co-immunoprecipitation (Co-IP). Our studies found that the expression of RUNX1 was upregulated in LF mice, and RUNX1 knockdown alleviated CCl4-induced LF. RUNX1 silencing reduced the viability and migration of HSCs. Besides, RUNX1, as a transcription factor, bound to the promoter of USP9X and regulated the expression of USP9X. USP9X is a deubiquitination enzyme and was found to be up-regulated in LF mice. USP9X silencing reduced the viability and migration of HSCs, thereby inhibiting LF. Further studies showed that USP9X could stabilize downstream Smad1 expression. Furthermore, we also found that RUNX1 regulated the expression of SMAD1 by transcriptionally activating the expression of USP9X, thereby regulating the activation of hepatic stellate cells and liver fibrosis.

Exogenous BMP9 promotes lung fibroblast HFL-1 cell activation via ALK1/Smad1/5 signaling in vitro

Bone morphogenetic protein 9 (BMP9) has recently been described as a crucial regulator in modulating fibroblast-type cell activation. Activin receptor-like kinase 1 (ALK1) is a high affinity receptor for BMP9 that exerts its role via Smad1/5. However, the functional roles of BMP9 in activating lung fibroblasts and the underlying signaling pathway are not completely understood. The present study aimed to explore the effect of exogenous BMP9 on human lung fibroblast HFL-1 cell proliferation and differentiation, as well as the potential role of the ALK1/Smad1/5 signaling pathway. In the present study, fibroblast proliferation was assessed using Cell Counting Kit-8 and colony formation assays, and the mRNA and protein expression of target genes was examined using reverse transcription-quantitative PCR and western blot assays, respectively. Compared with the control group, BMP9 treatment increased HFL-1 cell proliferation, mRNA and protein expression of differentiated markers, including α-smooth muscle actin, type I collagen and type III collagen, and the expression of ALK1 and phosphorylated Smad1/5 expression. Furthermore, the effects of BMP9 were partially rescued by dorsomorphin-1, an inhibitor of ALK1. The results indicated that BMP9 may serve as a key inducer of lung fibroblast activation and ALK1/Smad1/5 signaling might be associated with BMP9-mediated effects in HFL-1 cells. Therefore, the present study highlighted that the potential role of the BMP9/ALK1/Smad1/5 signaling pathway in the development of pulmonary fibrosis requires further investigation.

Potential roles of BMP9 in liver fibrosis

Liver fibrosis is a common phenomenon that is associated with several pathologies and is characterized by excessive extracellular matrix deposition that leads to progressive liver dysfunction. Bone morphogenetic protein 9 (BMP9) is the most recently discovered member of the BMP family. BMP9 bound with high affinity to activin receptor-like kinase 1 (ALK1) and endoglin in non-parenchymal liver cells. In addition, BMP9 activated Smad1/Smad5/Smad8 and induced the expression of the target genes inhibitor of differentiation 1 (Id1), hepcidin, Snail and the co-receptor endoglin in liver cells. Although the role of BMP9 in liver fibrosis is currently poorly understood, the presence of BMP9-activated proteins and its target genes have been reported to be associated with liver fibrosis development. This review summarizes the indirect connection between BMP9 and liver fibrosis, with a focus on the BMP9 signaling pathway members ALK1, endoglin, Id1, hepcidin and Snail. The observations on the role of BMP9 in regulating liver fibrosis may help in understanding the pathology mechanisms of liver disease. Furthermore, BMP9 could be served as a potent biomarker and the target of potential therapeutic drugs to treat hepatocytes fibrosis.

ALK1-Smad1/5 signaling pathway in fibrosis development: friend or foe?

Fibrosis is a common phenomenon associated with several pathologies, characterized by an excessive extracellular matrix deposition that leads to a progressive organ dysfunction. Thus fibrosis has a relevant role in chronic diseases affecting the kidney, the liver, lung, skin (scleroderma) and joints (arthritis), among others. The pathogenesis of fibrosis in different organs share numerous similarities, being one of them the presence of activated fibroblasts, denominated myofibroblast, which act as the main source of extracellular matrix proteins. Transforming growth factor beta-1 (TGF-β1) is a profibrotic cytokine that plays a pivotal role in fibrosis. The TGF-β1/ALK5/Smad3 signaling pathway has been studied in fibrosis extensively. However, an increasing number of studies involving the ALK1/Smad1 pathway in the fibrotic process exist. In this review we offer a perspective of the function of ALK1/Smad1 pathway in renal fibrosis, liver fibrosis, scleroderma and osteoarthritis, suggesting this pathway as a powerful therapeutical target. We also propose several strategies to modulate the activity of this pathway and its consequences in the fibrotic process.

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.

Alteration of protein glycosylation in human hepatic stellate cells activated with transforming growth factor-β1

Although aberrant glycosylation of human glycoproteins is related to liver fibrosis that results from chronic damage to the liver in conjunction with the activation of hepatic stellate cells (HSCs), little is known about the precision alteration of protein glycosylation referred to the activation of HSCs by transforming growth factor-β1 (TGF-β1). The human HSCs, LX-2 were activated by TGF-β1. The lectin microarrays were used to probe the alteration of protein glycosylation in the activated HSCs compared with the quiescent HSCs. Lectin histochemistry was used to further validate the lectin binding profiles and assess the distribution of glycosidic residues in cells. As a result, 14 lectins (e. g. AAL, PHA-E, ECA and ConA) showed increased signal while 7 lectins (e. g. UEA-I and GNA) showed decreased signal in the activated LX-2 compared with the quiescent LX-2. Meanwhile, AAL, PHA-E and ECA staining showed moderate binding to the cytoplasma membrane in the quiescent LX-2, and the binding intensified in the same regions of the activated LX-2. In conclusion, the precision alteration of protein glycosylation related to the activation of the HSCs may provide useful information to find new molecular mechanism of HSC activation and antifibrotic therapeutic strategies.

Expression and functional analysis of endoglin in isolated liver cells and its involvement in fibrogenic Smad signalling

Endoglin is an accessory component of the TGF-β-binding receptor complex that differentially modulates TGF-β and BMP responses. The existence of two splice variants L- and S-endoglin which differ in their cytoplasmic domain has already been shown in human and mice. Endoglin is located on the cell surfaces of cultured hepatic stellate cells and transdifferentiated myofibroblasts suggesting that this receptor might be associated with the profibrogenic attributes of these liver cell subpopulations. We now show that endoglin expression is increased in transdifferentiating hepatic stellate cells and in two models of liver fibrosis (i.e. bile duct ligation and carbon tetrachloride model) and further detectable in cultured portal fibroblasts representing another important fibrogenic cell type but not in hepatocytes. In respect to TGF-β1-signalling, we demonstrate that endoglin interacts with and is phosphorylated by TβRII. In hepatic stellate cells, TGF-β1 upregulates endoglin expression most likely via the ALK5 pathway and requires the SP1 transcription factor. We further identified a novel rat splice variant that is structurally and functionally different from that identified in human and mouse. Transient overexpression of endoglin resulted in a strong increase of TGF-β1-driven Smad1/5 phosphorylation and α-smooth muscle actin expression in a hepatic stellate cell line. In supernatants of respective cultures, we could detect the ectodomain of endoglin suggesting that shedding is a further key process involved in the regulation of this surface receptor.

Profiling protein markers associated with the sensitivity to concurrent chemoradiotherapy in human cervical carcinoma

Concurrent chemoradiotherapy (CCRT) is recently recommended as the primary and standard treatment modality for cervical cancer. The aim of this study is to investigate the protein biomarkers associated with CCRT sensitivity, so as to better understand the mechanisms underlying CCRT resistance. Fresh tumor tissues from five cases for each group of CCRT-highly sensitive (CCRT-HS) and CCRT-lowly sensitive (CCRT-LS) were analyzed by 2-D electrophoresis coupled with MALDI-TOF-MS, followed by Western blot for four candidate proteins including S100A9, galectin-7, nuclear matrix protein-238 (NMP-238), and heat shock protein-70 (HSP-70). In randomly selected CCRT-HS (n = 60) and CCRT-LS (n = 35) cases, these four differentially expressed proteins were detected by tissue microarray with immunohistochemistry staining to explore the association between these interested proteins and CCRT sensitivity. Nineteen proteins differentially expressed more than four times between two groups were identified. An association was revealed between CCRT sensitivity and increased S100A9 and galectin-7, but decreased NMP-238 and HSP-70 expression (p < 0.001, respectively). Although none of these four protein markers could be used as an independent predictive factor, a recurrence prediction model was generated by combining S100A9, galectin-7, NMP-238, and HSP-70 as a full predictive factor. The proteomic analysis combined with tissue microarray provides us a dramatic tool in predicting CCRT response. The increased expression of S100A9 and galectin-7, but decreased expression of NMP-238 and HSP-70, suggests a significantly increased sensitivity to CCRT in cervical cancer.

Construction of COL1A1-shRNA expression plasmid and screening of effective sequences to inhibit COL1A1 expression

AIM: To construct and select procollagen type 1 alpha 1 (COL1A1) short hairpin RNA (shRNA) expression plasmid that can inhibit COL1A1 mRNA expression in rat hepatic stellate cell (HSC).

METHODS: Rat COL1A1 cDNA sequence was obtained from NCBI website. Three small interfering RNA sequences were selected through online design of the Whitehead Institute. The corresponding double-stranded DNA was used to construct pGPU6/GFP/Neo plasmids, namely pGPU6/GFP/Neo-shRNA-A, pGPU6/GFP/Neo-shRNA-B and pGPU6/GFP/Neo-shRNA-C. HSC-T6 cells were transfected with a green fluorescent protein (GFP)-labeled siRNA to assess the transfection efficiency. To get most effective and optimal dosage siRNA, the three plasmids (1, 2, 3, 4 μg) were transfected into HSC-T6 cells with Lipofectamine 2000 respectively, and the untreated HSC-T6 cells were used as controls. The expression of COL1A1 mRNA was detected by reverse transcription-polymerase chain reaction (RT-PCR) after the most effective and optimal dosage was used.

RESULTS: The expression plasmids targeting on COL1A1 mRNA were successfully constructed, and confirmed by agarose electrophoresis and sequence analysis. The transfection efficiencies at a dose of 1, 2, 3, and 4 μg were approximately 16.7%, 20.3%, 23.5%, and 22.3%, and 2 μg was considered as the most optimal dosage in each group. The inhibitory rates of COL1A1 mRNA levels in the HSC-T6 cells transfected with pGPU6/GFP/Neo-shRNA-A, pGPU6/GFP/Neo-shRNA-B, and pGPU6/GFP/Neo-shRNA-C were 16.6%, 63.3%, and 80.3%, respectively, when 2 μg siRNA plasmid was used.

CONCLUSION: The constructed expression plasmid pGPU6/GFP/Neo-shRNA-C can effectively inhibit the expression of COL1A1 mRNA, providing a new method and material for the treatment of liver fibrosis.

Down-regulation of transforming growth factor β1/activin receptor-like kinase 1 pathway gene expression by herbal compound 861 is related to deactivation of LX-2 cells

AIM: To investigate the effect of herbal compound 861 (Cpd861) on the transforming growth factor-β1 (TGFβ1)/activin receptor-like kinase 1 (ALK1, type I receptor) signaling-pathway-related gene expression in the LX-2 cell line, and the inhibitory mechanism of Cpd861 on the activation of LX-2 cells.

METHODS: LX-2 cells were treated with TGFβ1 (5 ng/mL) Cpd861 (0.1 mg/mL), TGFβ1 (5 ng/mL) plus Cpd861 (5 ng/mL) for 24 h to investigate the effect of Cpd861 on the TGFβ1/ALK1 pathway. Real-time PCR was performed to examine the expression of α-SMA (α-smooth muscle actin), ALK1, Id1 (inhibitor of differentiation 1). Western blotting was carried out to measure the levels of α-SMA and phosphorylated Smad1, and immunocytochemical analysis for the expression of α-SMA.

RESULTS: In LX-2 cells, TGFβ1/ALK1-pathway-related gene expression could be stimulated by TGFβ1, which led to excessive activation of the cells. Cpd861 decreased the activation of LX-2 cells by reducing the expression of α-SMA mRNA and protein expression. This effect was related to inhibition of the above TGFβ1/ALK1-pathway-related expression of genes such as Id1 and ALK1, and phosphorylation of Smad1 in LX-2 cells, even with TGFβ1 co-treatment for 24 h.

CONCLUSION: Cpd861 can restrain the activation of LX-2 cells by inhibiting the TGFβ1/ALK1/Smad1 pathway.

Effect of cholinergic denervation on hepatic fibrosis induced by carbon tetrachloride in rats

Various factors involved in the development of liver fibrosis, including hepatic stellate cells (HSCs), cholinergic nervous activity and fibrogenetic cytokines. The present study aims to investigate the role of cholinergic regulation in the promoting of liver fibrogenesis relating to bone morphogenetic protein-6 (BMP-6) and/or transforming growth factor-beta1 (TGFbeta1). We treated carbon tetrachloride (CCl(4)) into rats for eight weeks to induce liver fibrosis and arranged these rats for cholinergic denervation, hepatic branch vagotomy or atropine administration. Acetylcholinesterase (AChE) staining showed the distribution of cholinergic nerve around fibrosis scaring septa. The immunohistochemical staining for alpha smooth muscle actin (alphaSMA) indicated the less HSCs in CCl(4) treated rat liver with cholinergic denervation as compared to the sham-operated CCl(4) treated rats. It seems that cholinergic nerve not only innervates around the fibrosis area but also promotes HSCs. We also detected TGFbeta1 and BMP-6 expressions using RT-PCR and immunohistochemistry. The obtained results show that cholinergic denerveration decreases BMP-6 and TGF-beta1 expressions in CCl(4) induced liver fibrosis of rats. In conclusion, cholinergic nerve may influence HSCs in addition to the lowering of BMP-6 and TGF-beta1 gene expressions to modify liver fibrosis.

TGF-beta1-induced cardiac myofibroblasts are nonproliferating functional cells carrying DNA damages

TGF-beta1 induces differentiation and total inhibition of cardiac MyoFb cell division and DNA synthesis. These effects of TGF-beta1 are irreversible. Inhibition of MyoFb proliferation is accompanied with the expression of Smad1, Mad1, p15Ink4B and total inhibition of telomerase activity. Surprisingly, TGF-beta1-activated MyoFbs are growth-arrested not only at G1-phase but also at S-phase of the cell cycle. Staining with TUNEL indicates that these cells carry DNA damages. However, the absolute majority of MyoFbs are non-apoptotic cells as established with two apoptosis-specific methods, flow cytometry and caspase-dependent cleavage of cytokeratin 18. Expression in MyoFbs of proliferative cell nuclear antigen even in the absence of serum confirms that these MyoFbs perform repair of DNA damages. These results suggest that TGF-beta1-activated MyoFbs can be growth-arrested by two checkpoints, the G1/S checkpoint, which prevents cells from entering S-phase and the intra-S checkpoint, which is activated by encountering DNA damage during the S phase or by unrepaired damage that escapes the G1/S checkpoint. Despite carrying of the DNA damages TGF-beta1-activated MyoFbs are highly functional cells producing lysyl oxidase and contracting the collagen matrix.

Corticotropin-releasing hormone activates connexin 43 via activator protein-1 transcription factor in human myometrial smooth muscle cells

Corticotropin-releasing hormone (CRH) and connexin 43 (Cx43) play crucial roles in uterine contraction and the onset of labor. The aim of the present study was to investigate the regulatory effects of CRH on Cx43 expression in human myometrial smooth muscle cells (SMCs) and, potentially, its activation of the c-Fos/activator protein (AP)-1 signaling pathway. Human myometrial SMCs collected from nonpregnant women were treated with different concentrations of CRH. Transient transfection of AP-1 decoy oligodeoxynucleotide (ODN) was used to block AP-1 sites of Cx43. The transcriptional activity of AP-1 was detected by luciferase assay. Cx43 protein expression was visualized by immunofluorescence staining. mRNA and protein expression of c-Fos and Cx43 were demonstrated by real-time quantitative RT-PCR and Western blot, respectively. CRH facilitated Cx43 expression and enhanced AP-1 promoter activity in human uterine SMCs. After CRH treatment, Cx43 expression in the cytoplasm increased significantly. CRH significantly increased mRNA and protein expression of c-Fos and Cx43 in a dose-dependent manner (P < 0.01). A transient transfection of AP-1 decoy ODN did not affect CRH regulation of c-Fos (P > 0.05) but almost completely abolished CRH-induced enhancement of Cx43 expression (P < 0.01). In human primary myometrial SMCs, CRH enhances Cx43 mRNA and protein expression through upregulation of c-Fos expression. Blockade of AP-1 sites to the Cx43 promoter can neutralize the CRH-induced upregulation of Cx43.