Smad2 and Smad3 play different roles in rat hepatic stellate cell function and alpha-smooth muscle actin organization

Cyclic strain alters the transcriptional and migratory response of scleral fibroblasts to TGFβ

In glaucoma, scleral fibroblasts are exposed to IOP-associated mechanical strain and elevated TGFβ levels. These stimuli, in turn, lead to scleral remodeling. Here, we examine the scleral fibroblast migratory and transcriptional response to these stimuli to better understand mechanisms of glaucomatous scleral remodeling. Human peripapillary scleral (PPS) fibroblasts were cultured on parallel grooves, treated with TGFβ (2 ng/ml) in the presence of vehicle or TGFβ signaling inhibitors, and exposed to uniaxial strain (1 Hz, 5%, 12-24 h). Axis of cellular orientation was determined at baseline, immediately following strain, and 24 h after strain cessation with 0° being completely aligned with grooves and 90° being perpendicular. Fibroblasts migration in-line and across grooves was assessed using a scratch assay. Transcriptional profiling of TGFβ-treated fibroblasts with or without strain was performed by RT-qPCR and pERK, pSMAD2, and pSMAD3 levels were measured by immunoblot. Pre-strain alignment of TGFβ-treated cells with grooves (6.2 ± 1.5°) was reduced after strain (21.7 ± 5.3°, p < 0.0001) and restored 24 h after strain cessation (9.5 ± 2.6°). ERK, FAK, and ALK5 inhibition prevented this reduction; however, ROCK, YAP, or SMAD3 inhibition did not. TGFβ-induced myofibroblast markers were reduced by strain (αSMA, POSTN, ASPN, MLCK1). While TGFβ-induced phosphorylation of ERK and SMAD2 was unaffected by cyclic strain, SMAD3 phosphorylation was reduced (p = 0.0004). Wound healing across grooves was enhanced by ROCK and SMAD3 inhibition but not ERK or ALK5 inhibition. These results provide insight into the mechanisms by which mechanical strain alters the cellular response to TGFβ and the potential signaling pathways that underlie scleral remodeling.

Arbidol attenuates liver fibrosis and activation of hepatic stellate cells by blocking TGF-β1 signaling

Chronic liver diseases (CLD) impact over 800 million people globally, causing about 2 million deaths annually. Arbidol (ARB), an indole-derivative used to treat influenza virus infection, was extensively used during COVID-19 pandemic in China. In recent years, studies have shown that ARB, compared to other antiviral drugs, exhibits greater liver-protective efficacy, indicating a potential hepatoprotective effect beyond its antiviral activity. However, the mechanism remains unclear. In this study, we investigated the impact of ARB on liver injury/fibrosis in bile duct ligated (BDL) mice and its effect on spontaneous and transforming growth factor β1 (TGF-β1)-induced activation of primary cultured hepatic stellate cells (HSCs). Oral administration of ARB significantly ameliorated BDL-induced liver injury/fibrosis as reflected by decreased serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), reduced collagen deposition, and diminished mRNA expression of fibrosis markers. ARB notably inhibited spontaneous and TGF-β1-induced activation of primary cultured HSCs. Moreover, ARB also drastically attenuated mRNA expression levels of platelet-derived growth factor receptor (Pdgfr), transforming growth factor-beta receptor (Tgfbr) 1, Tgfbr2, matrix metalloproteinase (Mmp)-2, and Mmp-9 in activated HSCs. We further demonstrate that ARB mitigated Smad2/3 phosphorylation in both TGF-β1 treated HSCs and BDL mice. These data together demonstrate that the therapeutic efficacy of ARB on liver fibrosis is independent of its antiviral activity and likely is achieved by blocking TGF-β1 signaling-mediated HSC activation.

Curcumin alleviates hypertrophic scarring by inhibiting fibroblast activation and regulating tissue inflammation

BACKGROUND

Hypertrophic scar (HS) that can lead to defects in appearance and function is often characterized by uncontrolled fibroblast proliferation and excessive inflammation. Curcumin has been shown to have anti-inflammatory and anti-oxidative effects and to play an anti-fibrotic role by interfering transforming growth factor-β1 (TGF-β1)/Smads signaling pathways.

AIM

To study the effect and mechanism of curcumin on HS from the perspective of fibroblast activity and inflammation regulation.

METHODS

Cell proliferation, migration and the expression of α-smooth muscle actin (α-SMA) of TGF-β1-induced human dermal fibroblasts (HDFs) treated by curcumin were evaluated using Cell Counting Kit-8 assay, 5-ethynyl-2'-deoxyuridine staining, Transwell assay, Western blotting and immunofluorescence, respectively. The expression of TGF-β1/Smad3 pathway-related molecules (TGF-β1, TGFβ-R1/2, p-Smad3, Smad4) was detected by Western blotting. In a rabbit ear model, hematoxylin and eosin and Masson's staining were conducted to assess scar elevation and collagen deposition, and immunohistochemistry was performed to detect the activation of fibroblasts and infiltration of inflammatory cells.

RESULTS

Curcumin inhibited proliferation, migration and α-SMA expression of HDFs in a dose-dependent manner. Curcumin (25 μm mol/L) did not regulate the expression of endogenous TGF-β1, but suppressed Smad3 phosphorylation and nuclear translocation, leading to lower α-SMA expression. Curcumin also reduced hypertrophic scarring of rabbit ear, accompanied by the inhibited TGF-β1/Smad3 pathway, inflammatory infiltration and M2 macrophage polarization.

CONCLUSION

Curcumin plays an anti-scar role through regulating fibroblast activation and tissue inflammation. Our findings provide scientific reference for the clinical use of curcumin in the treatment of HS.

Hepatic stellate cell-intrinsic role of SOCS1 in controlling hepatic fibrogenic response and the pro-inflammatory macrophage compartment during liver fibrosis

Introduction

Hepatic stellate cells (HSC) become activated, differentiate to myofibroblasts and produce extracellular fibrillar matrix during liver fibrosis. The hepatic fibrogenic response is orchestrated by reciprocal interactions between HSCs and macrophages and their secreted products. SOCS1 can regulate several cytokines and growth factors implicated in liver fibrosis. Here we investigated the role of SOCS1 in regulating HSC activation.

Methods

Mice lacking SOCS1 in HSCs (Socs1ΔHSC) were generated by crossing Socs1fl/fl and LratCre mice. Liver fibrosis was induced by carbon tetrachloride and evaluated by Sirius red staining, hydroxyproline content and immunostaining of myofibroblasts. Gene expression of pro-fibrogenic factors, cytokines, growth factors and chemokines were quantified by RT-qPCR. The phenotype and the numbers of intrahepatic leukocyte subsets were studied by flow cytometry. The impact of fibrosis on the development of diethyl nitrosamine-induced hepatocellular carcinoma was evaluated.

Results

Socs1ΔHSC mice developed more severe liver fibrosis than control Socs1fl/fl mice that was characterized by increased collagen deposition and myofibroblast differentiation. Socs1ΔHSC mice showed a significant increase in the expression of smooth muscle actin, collagens, matrix metalloproteases, cytokines, growth factors and chemokines in the liver following fibrosis induction. The fibrotic livers of Socs1ΔHSC mice displayed heightened inflammatory cell infiltration with increased proportion and numbers of Ly6ChiCCR2+ pro-inflammatory macrophages. This macrophage population contained elevated numbers of CCR2+CX3CR1+ cells, suggesting impaired transition towards restorative macrophages. Fibrosis induction following exposure to diethyl nitrosamine resulted in more numerous and larger liver tumor nodules in Socs1ΔHSC mice than in Socs1fl/fl mice.

Discussion

Our findings indicate that (i) SOCS1 expression in HSCs is a critical to control liver fibrosis and development of hepatocaellular carcinoma, and (ii) attenuation of HSC activation by SOCS1 regulates pro-inflammatory macrophage recruitment and differentiation during liver fibrosis.

3D collagen migration patterns reveal a SMAD3-dependent and TGF-β1-independent mechanism of recruitment for tumour-associated fibroblasts in lung adenocarcinoma

BACKGROUND

The TGF-β1 transcription factor SMAD3 is epigenetically repressed in tumour-associated fibroblasts (TAFs) from lung squamous cell carcinoma (SCC) but not adenocarcinoma (ADC) patients, which elicits a compensatory increase in SMAD2 that renders SCC-TAFs less fibrotic. Here we examined the effects of altered SMAD2/3 in fibroblast migration and its impact on the desmoplastic stroma formation in lung cancer.

METHODS

We used a microfluidic device to examine descriptors of early protrusions and subsequent migration in 3D collagen gels upon knocking down SMAD2 or SMAD3 by shRNA in control fibroblasts and TAFs.

RESULTS

High SMAD3 conditions as in shSMAD2 fibroblasts and ADC-TAFs exhibited a migratory advantage in terms of protrusions (fewer and longer) and migration (faster and more directional) selectively without TGF-β1 along with Erk1/2 hyperactivation. This enhanced migration was abrogated by TGF-β1 as well as low glucose medium and the MEK inhibitor Trametinib. In contrast, high SMAD2 fibroblasts were poorly responsive to TGF-β1, high glucose and Trametinib, exhibiting impaired migration in all conditions.

CONCLUSIONS

The basal migration advantage of high SMAD3 fibroblasts provides a straightforward mechanism underlying the larger accumulation of TAFs previously reported in ADC compared to SCC. Moreover, our results encourage using MEK inhibitors in ADC-TAFs but not SCC-TAFs.

[Hydroxynitone suppresses hepatic stellate cell activation by inhibiting TGF-β1 phosphorylation to alleviate CCl4-induced liver fibrosis in rats]

OBJECTIVE

To investigate the effect of hydronidone on CCl4-induced liver fibrosis in rats and explore the possible mechanism.

METHODS

Sixty-six male SD rats were randomized into 5 groups, including a control group (n=10), a liver fibrosis model group (n=20), 2 hydronidone dose groups (100 and 250 mg/kg; n=12), and a pirfenidone (250 mg/kg) treatment group (n= 12). Rat models of liver fibrosis were established by subcutaneous injection of CCl4 in all but the control group. Hydronidone and pirfenidone were given daily at the indicated doses by intragastric administration for 6 weeks. After the treatments, serum samples were collected from the rats for detecting liver function parameters, and hydroxyproline content in the liver tissue was determined. Inflammation and fibrosis in the liver tissue were observed using HE staining and Sirius Red staining. In the cell experiment, human hepatic stellate cell line LX-2 was stimulated with TGF-β1 and treated with hydronidone or pirfenidone, and the expression levels of α-SMA, collagen type I and phosphorylated Smad3, phosphorylated p38, phosphorylated ERK1/2 and phosphorylated Akt were detected with Western blotting.

RESULTS

In the rat models of liver fibrosis, treatment with hydronidone obviously improved the liver functions, reduced the content of hydroxyproline in the liver tissue, and significantly alleviated liver fibrosis (P < 0.05). In LX-2 cells, hydronidone dose-dependently decreased the expression levels of α-SMA and collagen type I. In TGF- β1-stimulated cells, the phosphorylation levels of Smad3, P38, ERK, and Akt increased progressively with the extension of the treatment time, but this effect was significantly attenuated by treatment with hydronidone (P < 0.05).

CONCLUSION

Hydronidone can inhibit the phosphorylation of the proteins in the TGF-β signaling pathway, thereby preventing TGF-β1-mediated activation of hepatic stellate cells, which may be a possible mechanism by which hydronidone alleviates CCl4-induced liver fibrosis in rats.

Evaluation of the Effects of Microgravity on Activated Primary Human Hepatic Stellate Cells

In recent years, research has been conducted to develop new medical treatments by simulating environments existing in space, such as zero-gravity. In this study, we evaluated the cell proliferation and gene expression of activated primary human hepatic stellate cells (HHSteCs) under simulated microgravity (SMG). Under SMG, cell proliferation was slower than in 1 G, and the evaluation of gene expression changes on day 1 of SMG by serial analysis of gene expression revealed the presence of Sirtuin, EIF2 signaling, hippo signaling, and epithelial adherence junction signaling. Moreover, reactive oxygen species were upregulated under SMG, and when N-acetyl-cystein was added, no difference in proliferation between SMG and 1 G was observed, suggesting that the oxidative stress generated by mitochondrial dysfunction caused a decrease in proliferation. Upstream regulators such as smad3, NFkB, and FN were activated, and cell-permeable inhibitors such as Ly294002 and U0126 were inhibited. Immunohistochemistry performed to evaluate cytoskeletal changes showed that more β-actin was localized in the cortical layer under SMG.

Dynamic regulatory module networks for inference of cell type-specific transcriptional networks

Changes in transcriptional regulatory networks can significantly alter cell fate. To gain insight into transcriptional dynamics, several studies have profiled bulk multi-omic data sets with parallel transcriptomic and epigenomic measurements at different stages of a developmental process. However, integrating these data to infer cell type–specific regulatory networks is a major challenge. We present dynamic regulatory module networks (DRMNs), a novel approach to infer cell type–specific cis-regulatory networks and their dynamics. DRMN integrates expression, chromatin state, and accessibility to predict cis-regulators of context-specific expression, where context can be cell type, developmental stage, or time point, and uses multitask learning to capture network dynamics across linearly and hierarchically related contexts. We applied DRMNs to study regulatory network dynamics in three developmental processes, each showing different temporal relationships and measuring a different combination of regulatory genomic data sets: cellular reprogramming, liver dedifferentiation, and forward differentiation. DRMN identified known and novel regulators driving cell type–specific expression patterns, showing its broad applicability to examine dynamics of gene regulatory networks from linearly and hierarchically related multi-omic data sets.

Mg-6Zn alloys promote the healing of intestinal anastomosis via TGF-β/Smad signaling pathway in regulation of collagen metabolism as compared with titanium alloys

There is a great clinical need for biodegradable materials. This study aimed to investigate the effects of Mg-6Zn and titanium alloy stapler nails on intestinal anastomosis healing mediated via the TGF-β/Smad signaling pathway, as reflected in collagen metabolism in rabbits. Side-to-side ileo-ileostomy was performed with linear stapler loaded with the two nails. The results showed that no obvious postoperative complications such as abdominal infection and anastomotic leakage were observed. General observation and scanning electron microscope showed that Mg-6Zn alloy nails remained intact in the first week, degraded significantly in the second week, and were little left in the third week, while the titanium alloy nails showed intact substrate throughout the experimental period. Immunohistochemical analysis showed that the expression of TGF-β1 in Mg-6Zn alloy group was higher than that in titanium alloy group after 1 week, but it increased slowly, arrived at a lower level in the third week. Collagen I showed an increased expression in Mg-6Zn alloy group, but decreased with time in titanium alloy group. An enhanced expression of collagen III in Mg-6Zn alloy group in the first week but much lower in the third week as compared to the titanium alloy group. The expression of smad2 in Mg-6Zn alloy group maintained a steady level, while in titanium alloy group it showed a general upward trend. The expression of smad3 in both groups held steady after 2 weeks, then in the third week, it showed a strong uptrend in Mg-6Zn alloy group, while decreased immediately in titanium alloy group. Our findings suggest that Mg-6Zn alloy nails degraded significantly within 3 weeks and could provide stability of intestinal anastomosis in the reconstruction of intestinal tract. TGF-β/Smad signaling pathway may play a role in regulation of baseline collagen synthesis throughout the process.

Effect of Hepatocyte Growth Factor-Transfected Human Umbilical Cord Mesenchymal Stem Cells on Hepatic Stellate Cells by Regulating Transforming Growth Factor-β1/Smads Signaling Pathway

Studies have shown that human umbilical cord mesenchymal stem cells (hUCMSCs) could ameliorate liver fibrosis (LF) through inhibiting the activation of hepatic stellate cells (HSCs). However, the specific mechanisms have not been studied clearly. The purpose of this study was to explore the possible mechanism of hepatocyte growth factor (HGF)-transfected hUCMSCs in inhibiting the proliferation and activation of HSCs-T6. The upper and lower double-cell coculture system was established among HGF-hUCMSCs, LV5-NC-hUCMSCs, hUCMSCs, and HSCs-T6 in experimental groups; HSCs-T6 were cultured alone as control group. After coculturing for 1, 2, and 3 days, results showed that HGF-transfected hUCMSCs could decrease cell viability of HSCs-T6 and promote apoptosis; inhibit their activation and reduce the expression of Collagen I, Collagen III, TGF-β1, Smad2 and Smad3, which may be related to inhibiting the activation of TGF-β1/Smads signaling pathway. These findings suggested that HGF-transfected hUCMSCs may be used as an alternative and novel therapeutic approach for the treatment of LF.

Prognostic value of small mother against decapentaplegic expression in human gastric cancer

Gastric cancer is the fifth most common malignancy in the world with alow 5-year survival rate. To date, no study has investigated the prognostic role of the small mother against decapentaplegic (SMAD) in gastric cancer. The association of SMADs with overall survival (OS) of gastric cancer was analyzed on the online Kaplan-Meier (KM) plotter database. Clinical data such as stage, differentiation, gender, treatment, and Her2 mutation status of gastric cancer patients were analyzed. The (E)-SIS3 was used to inhibit SMAD3 expression in gastric cancer cells, and the effects of SMAD3 on gastric cancer cells were analyzed via real-time cellular analysis (RTCA), flow cytometry, colony formation, and immunofluorescence assay. The results showed that the high expression of three members of SMADs (SMAD1, SMAD2, SMAD4) was correlated with afavorable OS of gastric cancer patients. Meanwhile, SMAD3 expression level indicated highly differentiated cancer. We also observed that surgical treatment was associated with high expression level of SMAD1 and SMAD2. Besides, the effect of Her2 on gastric cancer was not noticeable. Moreover, (E)-SIS3 pharmacological assay revealed that inhibition of expression of SMAD3 suppressed the proliferation and migration ability of gastric cancer cells via inducing apoptosis. Collectively, these results demonstrate that the high expression level of three members of SMADs (SMAD1, SMAD2, and SMAD4) is significantly correlated with favorable OS of gastric cancer patients, which is opposite to SMAD3. Thus, SMADs regulate the differentiation of cancer and can be used to guide treatment decisions.

Depletion of serotonin relieves concanavalin A-induced liver fibrosis in mice by inhibiting inflammation, oxidative stress, and TGF-β1/Smads signaling pathway

Serotonin exerts important functions in several liver pathophysiological processes. In this study, we investigated the role of serotonin in concanavalin A (Con A)-induced liver fibrosis (LF) in mice and the underlying mechanisms. To establish the mouse model of LF, mice of wild-type (WT) and tryptophan hydroxylase 1 (Tph1) knockout (serotonin depletion) received Con A for 8 successive weeks. Degree of fibrosis was assessed by Sirius red staining, as well as the measurements of alpha smooth muscle actin (α- SMA), hydroxyproline (Hyp) and type I collagen in liver tissues. To elucidate the potential mechanisms, we assessed the effect of serotonin depletion on inflammatory, oxidative stress as well as TGF-β1/Smads signaling pathway. We found that serotonin depletion significantly inhibited collagen deposition as evaluated by less collagenous fiber in Sirus Red staining and reduced contents of Hyp and type I collagen. In addition, the absence of serotonin significantly inhibited the release of several inflammatory cytokines, including interleukin-6 (IL-6), interferon-gamma (IFN-γ), tumor necrosis-alpha (TNF-α), and transforming growth factor β1 (TGF-β1). Oxidative stress was also largely mitigated in LF mice with serotonin deficiency as manifested by the decreases of oxidative stress markers (malonaldehyde (MDA) and myeloperoxidase (MPO)), as well as the increases of antioxidant stress indicators (glutathione (GSH), and GSH-px, catalase (CAT), superoxide dismutase (SOD)) in liver tissues. Moreover, the lack of serotonin may provide an antifibrotic role by inhibiting the intrahepatic expressions of TGF-β1, phosphorylated-smad2 (p-smad2), and phosphorylated-smad3 (p-smad3). These results indicated that, serotonin depletion attenuates Con A-induced LF through the regulation of inflammatory response, oxidative stress injury, and TGF-β1/Smads signaling pathway.

TGF-β1-driven reduction of cytoglobin leads to oxidative DNA damage in stellate cells during non-alcoholic steatohepatitis

BACKGROUND & AIMS

Cytoglobin (CYGB) is a respiratory protein that acts as a scavenger of reactive oxygen species. The molecular role of CYGB in human hepatic stellate cell (HSC) activation and human liver disease remains uncharacterised. The aim of this study was to reveal the mechanism by which the TGF-β1/SMAD2 pathway regulates the human CYGB promoter and the pathophysiological function of CYGB in human non-alcoholic steatohepatitis (NASH).

METHODS

Immunohistochemical staining was performed using human NASH biopsy specimens. Molecular and biochemical analyses were performed by western blotting, quantitative PCR, and luciferase and immunoprecipitation assays. Hydroxyl radicals (^•OH) and oxidative DNA damage were measured using an ^•OH-detectable probe and 8-hydroxy-2'-deoxyguanosine (8-OHdG) ELISA.

RESULTS

In culture, TGF-β1-pretreated human HSCs exhibited lower CYGB levels - together with increased NADPH oxidase 4 (NOX4) expression - and were primed for H₂O₂-triggered ^•OH production and 8-OHdG generation; overexpression of human CYGB in human HSCs reversed these effects. Electron spin resonance demonstrated the direct ^•OH scavenging activity of recombinant human CYGB. Mechanistically, pSMAD2 reduced CYGB transcription by recruiting the M1 repressor isoform of SP3 to the human CYGB promoter at nucleotide positions ⁺2-⁺13 from the transcription start site. The same repression did not occur on the mouse Cygb promoter. TGF-β1/SMAD3 mediated αSMA and collagen expression. Consistent with observations in cultured human HSCs, CYGB expression was negligible, but 8-OHdG was abundant, in activated αSMA⁺pSMAD2⁺- and αSMA⁺NOX4⁺-positive hepatic stellate cells from patients with NASH and advanced fibrosis.

CONCLUSIONS

Downregulation of CYGB by the TGF-β1/pSMAD2/SP3-M1 pathway brings about ^•OH-dependent oxidative DNA damage in activated hepatic stellate cells from patients with NASH.

LAY SUMMARY

Cytoglobin (CYGB) is a respiratory protein that acts as a scavenger of reactive oxygen species and protects cells from oxidative DNA damage. Herein, we show that the cytokine TGF-β1 downregulates human CYGB expression. This leads to oxidative DNA damage in activated hepatic stellate cells. Our findings provide new insights into the relationship between CYGB expression and the pathophysiology of fibrosis in patients with non-alcoholic steatohepatitis.

Administration of Steamed and Freeze-Dried Mature Silkworm Larval Powder Prevents Hepatic Fibrosis and Hepatocellular Carcinogenesis by Blocking TGF-β/STAT3 Signaling Cascades in Rats

Hepatocellular carcinoma (HCC) is the leading cause of cancer-related deaths worldwide and the majority of HCC patients occur with a background of hepatic fibrosis and cirrhosis. We have previously reported the hepatoprotective effects of steamed and freeze-dried mature silkworm larval powder (SMSP) in a chronic ethanol-treated rat model. Here, we assessed the anti-fibrotic and anti-carcinogenic effects of SMSP on diethylnitrosamine (DEN)-treated rats. Wistar rats were intraperitoneally injected with DEN once a week for 12 or 16 weeks with or without SMSP administration (0.1 and 1 g/kg). SMSP administration significantly attenuated tumor foci formation and proliferation in the livers of the rats treated with DEN for 16 weeks. SMSP administration also inhibited hepatic fibrosis by decreasing the levels of collagen fiber and the expression of pro-collagen I and alpha-smooth muscle actin (α-SMA). Moreover, SMSP supplementation improved the major parameters of fibrosis such as transforming growth factor-β (TGF-β), connective tissue growth factor (CTGF), tumor necrosis factor-alpha (TNF-α), plasminogen activator inhibitor-1 (PAI-1), and collagen type I (Col1A1) in the livers from the rats treated with DEN for 16 weeks. As s possible mechanisms, we investigated the effects of SMSP on the TGF-β and signal transducer and activator of transcription 3 (STAT3)-mediated signaling cascades, which are known to promote hepatic fibrosis. We found that SMSP treatment inhibited the activation of TGF-β and the phosphorylation of STAT3 pathway in DEN-treated rats. Moreover, SMSP administration suppressed the expressions of the target genes of TGF-β and STAT3 induced by DEN treatment. Our findings provide experimental evidences that SMSP administration has inhibitory effects of hepatic fibrosis and HCC induced by DEN in vivo and could be a promising strategy for the prevention or treatment of hepatic fibrosis and hepatocellular carcinogenesis.

Methanol extract of Iphiona aucheri ameliorates CCl4 induced hepatic injuries by regulation of genes in rats

We have investigated the protective potential of methanol extract of Iphiona aucheri (IAM) on the expression of endoplasmic reticulum (ER) stress associated genes and inflammatory genes on carbon tetrachloride (CCl4) induced hepatic toxicity in rats. Hepatic damage markers: aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and bilirubin were elevated while the content of antioxidants: catalase (CAT), superoxide dismutase (SOD), peroxidase (POD) and reduced glutathione (GSH) were decreased significantly (p < 0.05) in CCl4 treated rats as compared to the control group. The CCl4 intoxication induced a higher expression of glucose-regulated protein 78 kDa (GRP78), X-box-binding protein 1 total (XBP1t), spliced X-box-binding protein 1 (XBP1s), unspliced X-box-binding protein 1 (XBP1u), C/EBP homologous protein (CHOP) and genes involved in inflammation and fibrosis: tumor necrosis factor alpha (TNF-α), transforming growth factor-beta (TGF-β), mothers against DPP homolog 3 (SMAD3), alpha skeletal muscle actin (αSMA) and collagen type I alpha 1 chain (COL1A1). The intoxicated rats showed a low expression of the glutamate-cysteine ligase catalytic subunit (GCLC), protein disulfide isomerase (PDI) and nuclear factor (erythroid-derived 2) like-2 (Nrf2). The administration of IAM to intoxicated rats restored the expression of ER stress, inflammatory, fibrosis and antioxidant genes in a dose dependent manner. Our results indicated that IAM can impede the ER stress and inflammatory genes and it could be a complementary and alternative therapeutic agent for oxidative stress associated disorders.

Overexpression of miRNA-25-3p inhibits Notch1 signaling and TGF-β-induced collagen expression in hepatic stellate cells

During chronic liver injury hepatic stellate cells (HSCs), the principal source of extracellular matrix in the fibrotic liver, transdifferentiate into pro-fibrotic myofibroblast-like cells - a process potentially regulated by microRNAs (miRNAs). Recently, we found serum miRNA-25-3p (miR-25) levels were upregulated in children with Cystic Fibrosis (CF) without liver disease, compared to children with CF-associated liver disease and healthy individuals. Here we examine the role of miR-25 in HSC biology. MiR-25 was detected in the human HSC cell line LX-2 and in primary murine HSCs, and increased with culture-induced activation. Transient overexpression of miR-25 inhibited TGF-β and its type 1 receptor (TGFBR1) mRNA expression, TGF-β-induced Smad2 phosphorylation and subsequent collagen1α1 induction in LX-2 cells. Pull-down experiments with biotinylated miR-25 revealed Notch signaling (co-)activators ADAM-17 and FKBP14 as miR-25 targets in HSCs. NanoString analysis confirmed miR-25 regulation of Notch- and Wnt-signaling pathways. Expression of Notch signaling pathway components and endogenous Notch1 signaling was downregulated in miR-25 overexpressing LX-2 cells, as were components of Wnt signaling such as Wnt5a. We propose that miR-25 acts as a negative feedback anti-fibrotic control during HSC activation by reducing the reactivity of HSCs to TGF-β-induced collagen expression and modulating the cross-talk between Notch, Wnt and TGF-β signaling.

Engineered Fibrous Networks To Investigate the Influence of Fiber Mechanics on Myofibroblast Differentiation

Tissue fibrosis is a leading cause of mortality and is characterized by excessive protein deposition and altered tissue mechanical properties. In pathological fibrosis, as well as cancer related fibrosis, tissue pericytes and fibroblasts transition from a quiescent to a myofibroblastic phenotype. In vitro models are needed to better understand how these cells are influenced by their local microenvironment. Here, we developed a fibrous network platform to mimic the structure of the extracellular matrix, where fibers consist of cross-linked hyaluronic acid hydrogels with controlled cross-link density and mechanical properties. As a model myofibroblast precursor, primary hepatic stellate cells were seeded onto fibers with either low (soft) or high (stiff) cross-link density, either directly after isolation (quiescent) or following preculture on tissue culture plates (activated). In general, both quiescent and activated cells showed an increase in spreading, alpha smooth muscle actin expression, and the formation of multicellular clusters on soft fibers when compared to stiff fibers. Further, inhibition of alpha smooth muscle actin decreased activation of cells on soft fibers. This is likely due to fiber recruitment in soft fibers that increased local fiber density, whereas stiff fibers resisted recruitment. This work emphasizes the importance of substrate topography on cell-material interactions and shows that tunable fibrous hydrogels are a relevant culture platform for studying fibrosis and mechanotransduction in disease.

Antifibrotics in liver disease: are we getting closer to clinical use?

The process of wound healing in response to chronic liver injury leads to the development of liver fibrosis. Regardless of etiology, the profound impact of the degree of liver fibrosis on the prognosis of chronic liver diseases has been well demonstrated. While disease-specific therapy, such as treatments for viral hepatitis, has been shown to reverse liver fibrosis and cirrhosis in both clinical trials and real-life practice, subsets of patients do not demonstrate fibrosis regression. Moreover, where disease-specific therapies are not available, the need for antifibrotics exists. Increased understanding into the pathogenesis of liver fibrosis sets the stage to focus on antifibrotic therapies attempting to: (1) Minimize liver injury and inflammation; (2) Inhibit liver fibrogenesis by enhancing or inhibiting target receptor-ligand interactions or intracellular signaling pathways; and (3) Promote fibrosis resolution. While no antifibrotic therapies are currently available, a number are now being evaluated in clinical trials, and their use is becoming closer to reality for select subsets of patients.

Knockdown of LOXL1 inhibits TGF-β1-induced proliferation and fibrogenesis of hepatic stellate cells by inhibition of Smad2/3 phosphorylation

Liver fibrosis is pathological condition that seriously threatens human health. The lysyl oxidase (LOX) family has been reported to promote liver fibrosis. However, the effect of LOX-like 1 (LOXL1), a member of LOX family, on fibrogenesis of hepatic stellate cells (HSCs) remains unknown. The current study aimed to investigate the role of LOXL1 in liver fibrosis and the potential mechanism. We found that the mRNA and protein levels of LOXL1 were increased in transforming growth factor-beta 1 (TGF-β1)-stimulated human hepatic stellate cell line LX-2. Knockdown of LOXL1 inhibited the proliferation of TGF-β1-stimulated LX-2 cells. Knockdown of LOXL1 suppressed TGF-β1-induced expression of metalloproteinase type 1 (TIMP1), α-smooth muscle actin (α-SMA), and collagen type I (Col-I), as well as phosphorylation of Smad2 and Smad3 in LX-2 cells. In addition, the cell proliferation and fibrogenesis mediated by TGF-β1 stimulation and LOXL1 overexpression were abolished by knockdown of Smad2 and Smad3. Collectively, knockdown of LOXL1 suppressed cell proliferation and fibrogenesis in TGF-β1-stimulated HSCs via regulating the phosphorylation of Smad2/3.

Valproic Acid Induces Endothelial-to-Mesenchymal Transition-Like Phenotypic Switching

Valproic acid (VPA), a histone deacetylase (HDAC) inhibitor, is a widely used anticonvulsant drug that is currently undergoing clinical evaluation for anticancer therapy due to its anti-angiogenic potential. Endothelial cells (ECs) can transition into mesenchymal cells and this form of EC plasticity is called endothelial-to-mesenchymal transition (EndMT), which is widely implicated in several pathologies including cancer and organ fibrosis. However, the effect of VPA on EC plasticity and EndMT remains completely unknown. We report herein that VPA-treatment significantly inhibits tube formation, migration, nitric oxide production, proliferation and migration in ECs. A microscopic evaluation revealed, and qPCR, immunofluorescence and immunoblotting data confirmed EndMT-like phenotypic switching as well as an increased expression of pro-fibrotic genes in VPA-treated ECs. Furthermore, our data confirmed important and regulatory role played by TGFβ-signaling in VPA-induced EndMT. Our qPCR array data performed for 84 endothelial genes further supported our findings and demonstrated 28 significantly and differentially regulated genes mainly implicated in angiogenesis, endothelial function, EndMT and fibrosis. We, for the first time report that VPA-treatment associated EndMT contributes to the VPA-associated loss of endothelial function. Our data also suggest that VPA based therapeutics may exacerbate endothelial dysfunction and EndMT-related phenotype in patients undergoing anticonvulsant or anticancer therapy, warranting further investigation.

Anti-inflammatory properties of ursodeoxycholyl lysophosphatidylethanolamide in endotoxin-mediated inflammatory liver injury

AIM

Endotoxin-mediated liver inflammation is a key component of many acute and chronic liver diseases contributing to liver damage, fibrosis and eventually organ failure. Here, we investigated ursodeoxycholyl lysophosphatidylethanolamide (UDCA-LPE), a synthetic bile acid-phospholipid conjugate regarding its anti-inflammatory and anti-fibrogenic properties.

METHODS

Anti-inflammatory properties of UDCA-LPE were evaluated in a mouse model of D-galactosamine/lipopolysaccharide (GalN/LPS)-induced acute liver injury, LPS treated RAW264.7 macrophages and murine primary Kupffer cells. Furthermore, anti-inflammatory and anti-fibrotic effects of UDCA-LPE were studied on primary hepatic stellate cells (HSC) incubated with supernatant from LPS±UDCA-LPE treated RAW264.7 cells.

RESULTS

UDCA-LPE ameliorated LPS-induced increase of IL-6, TNF-α, TGF-β, NOX-2 in the GalN/LPS model by up to 80.2% for IL-6. Similarly, UDCA-LPE markedly decreased the expression of inflammatory cytokines IL-6, TNF-α and TGF-β as well as the chemokines MCP1 and RANTES in LPS-stimulated RAW 264.7 cells. Anti-inflammatory effects were also observed in primary murine Kupffer cells. Mechanistic evaluation revealed a reversion of LPS-activated pro-inflammatory TLR4 pathway by UDCA-LPE. Moreover, UDCA-LPE inhibited iNOS and NOX-2 expression while activating eNOS via phosphorylation of AKT and pERK1/2 in RAW264.7 cells. HSC treated with conditioned medium from LPS±UDCA-LPE RAW264.7 cells showed lower fibrogenic activation due to less SMAD2/3 phosphorylation, reduced expression of profibrogenic CTGF and reduced pro-inflammatory chemokine expression.

CONCLUSION

In the setting of endotoxin-mediated liver inflammation, UDCA-LPE exerts profound anti-inflammatory and anti-fibrotic effect implying a promising potential for the drug candidate as an experimental approach for the treatment of acute and chronic liver diseases.

Role of Smad3 signaling in the epithelial‑mesenchymal transition of the lens epithelium following injury

Transforming growth factor-β (TGF-β) is important in the development of posterior capsule opacification (PCO), and inhibition of the TGF-β pathway may represent a novel method of treating PCO. Drosophila protein, mothers against decapentaplegic homolog 3 (Smad3) is a phosphorylated receptor-activated Smad required for the transmission of TGF-β signals. Smad3 knockout (KO) disturbs the activation of TGF-β signaling, thus inhibiting the onset of PCO. In the present study, lens epithelial cell (LEC) damage induced by extracapsular cataract extraction was simulated by puncture of the anterior capsule using a 26-gauge hypodermic needle. The effect of Smad3 in the trauma-induced epithelial-mesenchymal transition (EMT) of the lens epithelium in Smad3-KO and wild-type (WT) mice was then observed. The expression levels of EMT markers and extracellular matrix components were measured in the two groups by reverse transcription-quantitative polymerase chain reaction analysis, western blot analysis and immunofluorescence staining. Apoptosis was also detected in the punctured anterior capsule. The Smad3-KO mice exhibited lower expression levels of α-smooth muscle actin, lumican, osteopontin, fibronectin and collagen, compared with the WT mice. Additionally, the Smad3-KO mice exhibited a higher percentage of apoptotic cells than the WT mice. Smad3 signaling was associated with the induction of trauma-induced EMT, and Smad3 KO interfered with TGF-β signaling pathway activation, but did not completely inhibit the trauma-induced EMT in LECs. Therefore, Smad3 may be a target in the treatment of PCO and other fibrosis-related diseases.

Rapamycin Inhibits the Growth and Collagen Production of Fibroblasts Derived from Human Urethral Scar Tissue

Rapamycin can inhibit fibroblast proliferation, collagen accumulation, and urethral stricture in rabbits. Transforming growth factor-beta-1 (TGF-β1) signaling, with downstream recruitment of Smad2, is known to promote fibrosis. This in vitro study examined the effects of rapamycin on fibroblasts derived from human urethral scar tissue (FHUS) and investigated the possible mechanism with respect to regulation of TGF-β1 signaling. FHUS were cultured from urethral scar tissues collected from four patients with urethral stricture. The cells were exposed to different concentrations of rapamycin (0, 10, 20, 40, 80, or 160 ng/ml) for 24 or 48 hours. Cell growth was assessed by the MTT assay. Collagen content was measured based on hydroxyproline levels. The mRNA expressions of Smad2, eIF-4E, and alpha-1 chains of collagen types I and III (Col1α1 and Col3α1) were determined by semiquantitative reverse-transcription PCR. The protein expressions of Smad2, phospho-Smad2, and eIF-4E were evaluated by western blot. Rapamycin caused a concentration-dependent inhibition of FHUS growth at 24 and 48 hours (P < 0.01). Rapamycin decreased total collagen content (P < 0.01), collagen content per 10⁵ cells (P < 0.05), and mRNA expressions of Col1α1 and Col3α1 (P < 0.05) in a concentration-dependent manner. Rapamycin elicited concentration-dependent reductions in the mRNA (P < 0.05) and protein (P < 0.01) expressions of Smad2 and eIF-4E. The two highest concentrations of rapamycin also enhanced phospho-Smad2 levels (P < 0.01). In conclusion, the present study confirmed that rapamycin may reduce the growth and collagen production of FHUS, possibly through inhibition of TGF-β1 signaling.

Andrographolide Ameliorates Liver Fibrosis in Mice: Involvement of TLR4/NF-κB and TGF-β1/Smad2 Signaling Pathways

Liver fibrosis is characterized by activated hepatic stellate cells (HSC) and extracellular matrix accumulation. Blocking the activation of HSC and the inflammation response are two major effective therapeutic strategies for liver fibrosis. In addition to the long history of using andrographolide (Andro) for inflammatory disorders, we aimed at elucidating the pharmacological effects and potential mechanism of Andro on liver fibrosis. In this study, liver fibrosis was induced by carbon tetrachloride (CCl₄) and the mice were intraperitoneally injected with Andro for 6 weeks. HSC cell line (LX-2) and primary HSC were also treated with Andro in vitro. Treatment of CCl₄-induced mice with Andro decreased the levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), Sirius red staining as well as the expression of α smooth muscle actin (α-SMA) and transforming growth factor- (TGF-) β1. Furthermore, the expression of Toll-like receptor (TLR)4 and NF-κB p50 was also inhibited by Andro. Additionally, in vitro data confirmed that Andro treatment not only attenuated the expression of profibrotic and proinflammatory factors but also blocked the TGF-β1/Smad2 and TLR4/NF-κB p50 pathways. These results demonstrate that Andro prevents liver inflammation and fibrosis, which is in correlation with the inhibition of the TGF-β1/Smad2 and TLR4/NF-κB p50 pathways, highlighting Andro as a potential therapeutic strategy for liver fibrosis.

肝纤维化逆转机制的研究进展及治疗概况

肝纤维化是肝脏对慢性损伤的一种修复反应, 多是持续性肝脏损伤或纤维化刺激因子刺激产生的共有病理改变, 是一项严重的全球性健康难题. 近年来临床研究发现, 由病毒性肝炎造成肝纤维化或肝硬化的患者, 在成功接受病毒性肝炎治疗后, 其肝纤维化甚至肝硬化发生了逆转现象. 因此研究和了解肝纤维化逆转的机制有利于发现新的针对肝纤维化的治疗靶向. 本文就近年来有关肝纤维化逆转机制的研究以及治疗概况作一综述, 以期为肝纤维化的研究提供帮助.

SMAD3 and SMAD4 have a more dominant role than SMAD2 in TGFβ-induced chondrogenic differentiation of bone marrow-derived mesenchymal stem cells

To improve cartilage formation by bone marrow-derived mesenchymal stem cells (BMSCs), the signaling mechanism governing chondrogenic differentiation requires better understanding. We previously showed that the transforming growth factor-β (TGFβ) receptor ALK5 is crucial for chondrogenesis induced by TGFβ. ALK5 phosphorylates SMAD2 and SMAD3 proteins, which then form complexes with SMAD4 to regulate gene transcription. By modulating the expression of SMAD2, SMAD3 and SMAD4 in human BMSCs, we investigated their role in TGFβ-induced chondrogenesis. Activation of TGFβ signaling, represented by SMAD2 phosphorylation, was decreased by SMAD2 knockdown and highly increased by SMAD2 overexpression. Moreover, TGFβ signaling via the alternative SMAD1/5/9 pathway was strongly decreased by SMAD4 knockdown. TGFβ-induced chondrogenesis of human BMSCs was strongly inhibited by SMAD4 knockdown and only mildly inhibited by SMAD2 knockdown. Remarkably, both knockdown and overexpression of SMAD3 blocked chondrogenic differentiation. Chondrogenesis appears to rely on a delicate balance in the amount of SMAD3 and SMAD4 as it was not enhanced by SMAD4 overexpression and was inhibited by SMAD3 overexpression. Furthermore, this study reveals that TGFβ-activated phosphorylation of SMAD2 and SMAD1/5/9 depends on the abundance of SMAD4. Overall, our findings suggest a more dominant role for SMAD3 and SMAD4 than SMAD2 in TGFβ-induced chondrogenesis of human BMSCs.

Differentially expressed microRNAs in the corpus cavernosum from a murine model with type 2 diabetes mellitus-associated erectile dysfunction

To better understand the molecular aetiology of type 2 diabetes mellitus-associated erectile dysfunction (T2DMED) and to provide candidates for further study of its diagnosis and treatment, this study was designed to investigate differentially expressed microRNAs (miRNAs) in the corpus cavernosum (CC) of mice with T2DMED using GeneChip array techniques (Affymetrix miRNA 4.0 Array) and to predict target genes and signalling pathways regulated by these miRNAs based on bioinformatic analysis using TargetScan, the DAIAN web platform and DAVID. In the initial screening, 21 miRNAs appeared distinctly expressed in the T2DMED group (fold change ≥3, p ≤ 0.01). Among them, the differential expression of miR-18a, miR-206, miR-122, and miR-133 were confirmed by qRT-PCR (p < 0.05 and FDR <5 %). According to bioinformatic analysis, the four miRNAs were speculated to play potential roles in the mechanisms of T2DMED via regulating 28 different genes and several pathways, including apoptosis, fibrosis, eNOS/cGMP/PKG, and vascular smooth muscle contraction processes, which mainly focused on influencing the functions of the endothelium and smooth muscle in the CC. IGF-1, as one of the target genes, was verified to decrease in the CCs of T2DMED animals via ELISA and was confirmed as the target of miR-18a or miR-206 via luciferase assay. Finally, these four miRNAs deserve further confirmation as biomarkers of T2DMED in larger studies. Additionally, miR-18a and/or miR-206 may provide new preventive/therapeutic targets for ED management by targeting IGF-1.

MiR-10a improves hepatic fibrosis by regulating the TGFβl/Smads signal transduction pathway

The aim of the present study was to examine the expression variation of the mouse hepatic fibrosis tissue transforming growth factor (TGF)-βl/Smads signal transduction pathway and its correlation with progression of hepatic fibrosis. The promotion effect of microRNA (miR)-10a on hepatic fibrosis and its possible mechanism was also assessed. Forty healthy female 8-week-old C57BL6/J mice were randomly divided into the control group (intraperitoneal injection of 5 µl/g normal saline, twice per week for 8 weeks) and the hepatic fibrosis group (intraperitoneal injection of 5 µl/g 10% CCI4 olive oil, twice per week for 8 weeks), with 20 mice per group. RT-PCR was used to test miR-10a expression in cells in the control and hepatic fibrosis groups. Cell culture and transfection of miR-10a mimics were conducted in the two groups and a Cell Counting Kit-8 was used to test the expression of TGF-β1 and Smad7 in hepatic fibroblasts. It was found that in comparison with the control group, miR-10a expression was significantly increased in the hepatic fibrosis group compared with the control group (P<0.05). The expression quantity of miR-10a was significantly increased in the transfection group compared with the control group (P<0.05). A high expression of miR-10a significantly improved TGF-β1 expression and reduced Smad7 expression in the hepatic fibrosis group (P<0.05). In conclusion, miR-10a expression was high in mouse hepatic tissues, transfection of miR-10a mimics significantly promoted the cell proliferation of hepatic fibrosis, and miR-10a improved hepatic fibrosis by regulating the TGF-βl/Smads signal transduction pathway.

Screening for and validation of a hepatic fibrosis-related pathway induced by insulin-like growth factor-binding protein-related protein 1

OBJECTIVE

Our previous studies characterized insulin-like growth factor-binding protein-related protein 1 (IGFBPrP1) as a molecule that promotes hepatic fibrogenesis, but its mechanism has not been fully elucidated. Here, we have investigated the effect of IGFBPrP1 on gene expression in the hepatic fibrosis-related pathway.

MATERIALS AND METHODS

Sprague-Dawley rats received injections of an adenovirus carrying IGFBPrP1 or EGFP cDNA into their tail veins. In hepatic preparations, hepatic stellate cell activation was determined by α-smooth muscle actin expression and hepatic fibrosis by Sirius red staining and hydroxyproline content analysis. IGFBPrP1-inducible genes of the hepatic fibrosis-related pathway were assessed by PCR array. Expression of IGFBPrP1 and transforming growth factor β1 (TGFβ1) and array results were evaluated by quantitative real-time PCR and western blotting.

RESULTS

IGFBPrP1-overexpressing rats showed an increase in α-smooth muscle actin expression and collagen and hydroxyproline content in the liver. The PCR array results indicated that some genes were upregulated and some were downregulated in Ad-IGFBPrP1-infected rats. Among these, Egr1, MAP2K2 (MEK2) and MAPK3 (ERK1) expression increased, whereas PTEN and Hhip mRNA expression decreased. Egr1 protein levels increased and peaked 2 weeks after infection and then decreased gradually. PTEN protein decreased gradually in Ad-IGFBPrP1-infected rats with a concurrent increase in the degree of hepatic fibrosis. TGFβ1 levels increased during hepatic fibrosis development in liver tissues.

CONCLUSION

Egr1, PTEN, Hhip, MAP2K2 (MEK2) and MAPK3 (ERK1) were identified as candidate genes of the IGFBPrP1-induced hepatic fibrosis-related pathway. IGFBPrP1 promoted hepatic fibrosis mainly by enhancing the TGFβ1 expression that it triggered.

Gradually softening hydrogels for modeling hepatic stellate cell behavior during fibrosis regression

The extracellular matrix (ECM) presents an evolving set of mechanical cues to resident cells. We developed methacrylated hyaluronic acid (MeHA) hydrogels containing both stable and hydrolytically degradable crosslinks to provide cells with a gradually softening (but not fully degradable) milieu, mimicking physiological events such as fibrosis regression. To demonstrate the utility of this cell culture system, we studied the phenotype of rat hepatic stellate cells, the major liver precursors of fibrogenic myofibroblasts, within this softening environment. Stellate cells that were mechanically primed on tissue culture plastic attained a myofibroblast phenotype, which persisted when seeded onto stiff (∼20 kPa) hydrogels. However, mechanically primed stellate cells on stiff-to-soft (∼20 to ∼3 kPa) hydrogels showed reversion of the myofibroblast phenotype over 14 days, with reductions in cell area, expression of the myofibroblast marker alpha-smooth muscle actin (α-SMA), and Yes-associated protein/Transcriptional coactivator with PDZ-binding motif (YAP/TAZ) nuclear localization when compared to stellate cells on stiff hydrogels. Cells on stiff-to-soft hydrogels did not fully revert, however. They displayed reduced expression of glial fibrillary acidic protein (GFAP), and underwent abnormally rapid re-activation to myofibroblasts in response to re-stiffening of the hydrogels through introduction of additional crosslinks. These features are typical of stellate cells with an intermediate phenotype, reported to occur in vivo with fibrosis regression and re-injury. Together, these data suggest that mechanics play an important role in fibrosis regression and that integrating dynamic mechanical cues into model systems helps capture cell behaviors observed in vivo.

The rationale for targeting TGF-β in chronic liver diseases

BACKGROUND

Transforming growth factor (TGF)-β is a pluripotent cytokine that displays several tissue-specific biological activities. In the liver, TGF-β is considered a fundamental molecule, controlling organ size and growth by limiting hepatocyte proliferation. It is involved in fibrogenesis and, therefore, in worsening liver damage, as well as in triggering the development of hepatocellular carcinoma (HCC). TGF-β is known to act as an oncosuppressor and also as a tumour promoter in HCC, but its role is still unclear.

DESIGN

In this review, we discuss the potential role of TGF-β in regulating the tumoural progression of HCC, and therefore the rationale for targeting this molecule in patients with HCC.

RESULTS

A considerable amount of experimental preclinical evidence suggests that TGF-β is a promising druggable target in patients with HCC. To support this hypothesis, a phase II clinical trial is currently ongoing using a TGF-β pathway inhibitor, and results will soon be available.

CONCLUSIONS

The identification of new TGF-β related biomarkers will help to select those patients most likely to benefit from therapy aimed at inhibiting the TGF-β pathway. New formulations that may provide a more controlled and sustained delivery of the drug will improve the therapeutic success of such treatments.

Long noncoding RNAs expressed in human hepatic stellate cells form networks with extracellular matrix proteins

BACKGROUND

Hepatic fibrosis is the underlying cause of cirrhosis and liver failure in nearly every form of chronic liver disease, and hepatic stellate cells (HSCs) are the primary cell type responsible for fibrosis. Long noncoding RNAs (lncRNAs) are increasingly recognized as regulators of development and disease; however, little is known about their expression in human HSCs and their function in hepatic fibrosis.

METHODS

We performed RNA sequencing and ab initio assembly of RNA transcripts to define the lncRNAs expressed in human HSC myofibroblasts. We analyzed chromatin immunoprecipitation data and expression data to identify lncRNAs that were regulated by transforming growth factor beta (TGF-β) signaling, associated with super-enhancers and restricted in expression to HSCs compared with 43 human tissues and cell types. Co-expression network analyses were performed to discover functional modules of lncRNAs, and principle component analysis and K-mean clustering were used to compare lncRNA expression in HSCs with other myofibroblast cell types.

RESULTS

We identified over 3600 lncRNAs that are expressed in human HSC myofibroblasts. Many are regulated by TGF-β, a major fibrotic signal, and form networks with genes encoding key components of the extracellular matrix (ECM), which is the substrate of the fibrotic scar. The lncRNAs directly regulated by TGF-β signaling are also enriched at super-enhancers. More than 400 of the lncRNAs identified in HSCs are uniquely expressed in HSCs compared with 43 other human tissues and cell types and HSC myofibroblasts demonstrate different patterns of lncRNA expression compared with myofibroblasts originating from other tissues. Co-expression analyses identified a subset of lncRNAs that are tightly linked to collagen genes and numerous proteins that regulate the ECM during formation of the fibrotic scar. Finally, we identified lncRNAs that are induced during progression of human liver disease.

CONCLUSIONS

lncRNAs are likely key contributors to the formation and progression of fibrosis in human liver disease.

Stiffening hydrogels for investigating the dynamics of hepatic stellate cell mechanotransduction during myofibroblast activation

Tissue fibrosis contributes to nearly half of all deaths in the developed world and is characterized by progressive matrix stiffening. Despite this, nearly all in vitro disease models are mechanically static. Here, we used visible light-mediated stiffening hydrogels to investigate cell mechanotransduction in a disease-relevant system. Primary hepatic stellate cell-seeded hydrogels stiffened in situ at later time points (following a recovery phase post-isolation) displayed accelerated signaling kinetics of both early (Yes-associated protein/Transcriptional coactivator with PDZ-binding motif, YAP/TAZ) and late (alpha-smooth muscle actin, α-SMA) markers of myofibroblast differentiation, resulting in a time course similar to observed in vivo activation dynamics. We further validated this system by showing that α-SMA inhibition following substrate stiffening resulted in attenuated stellate cell activation, with reduced YAP/TAZ nuclear shuttling and traction force generation. Together, these data suggest that stiffening hydrogels may be more faithful models for studying myofibroblast activation than static substrates and could inform the development of disease therapeutics.

Smad2 increases the apoptosis of activated human hepatic stellate cells induced by TRAIL

The activation of hepatic stellate cells (HSCs) plays a critical role in the development of liver fibrosis. The induction of apoptosis in activated HSCs during the recovery phase of hepatic fibrosis represents a potential anti-fibrotic therapy. We have previously shown that Smad2 protects against hepatic fibrogenesis; however, the role of Smad2 in the regulation of activated HSC apoptosis remains unknown. We hypothesized that Smad2 regulates the apoptosis of activated HSCs, leading to the resolution of liver fibrosis. To test this hypothesis, the livers of rats were harvested at 0 and 4 weeks after hepatic fibrosis was established by CCl4 injection. Furthermore, TGF-β1-activated HSCs were treated with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) following the silencing or overexpression of Smad2. Both the phosphorylation of Smad2 and TRAIL were detected in fibrotic liver tissues. The results of TUNEL and α-SMA double-staining showed an increase in the apoptosis of activated HSCs during the spontaneous recovery phase. The knockdown of Smad2 reduced TRAIL-induced apoptosis in TGF-β1-activated human LX-2 cells and resulted in an increased expression of α-SMA and collagen I (Col. I). In contrast, the overexpression of Smad2 increased TRAIL-induced HSC apoptosis and reduced the expression of α-SMA and Col. I. The mechanisms underlying these findings were associated with the Smad2-mediated down-regulation of X-linked inhibitor of apoptosis protein (XIAP), resulting in enhanced caspase-3 activity and apoptosis. In conclusion, Smad2 enhances TRAIL-induced apoptosis in activated HSCs, which facilitates the resolution of hepatic fibrosis.

Effect of total flavone from Litchi chinensis Sonn on Smad3, Smad4 and TIMP-1 expression in a rat model of liver fibrosis

AIM: To observe the effect of total flavone from Litchi chinensis Sonn (TFL) on dimethylnitrosamine (DMN) induced hepatic fibrosis and the expression of Smad3, Smad4 and TIMP-1 in rat liver tissue, to explore the antifibrotic mechanism of TFL.

METHODS: Ninety male SD rats were randomly divided into a normal control group, a fibrosis model group, a colchicine positive control group, and high-, medium-, and low-dose TFL groups [200, 100, and 50 mg/(kg•d), respectively]. Liver fibrosis was induced in rats by intraperitoneal injection of 0.5% DMN solution. Colchicine or TFL was given during modelling by gavage, once a day, for 6 wk. Rats were killed after 6 wk, and the levels of alanine aminotransferase (ALT) and aspartate transaminase (AST) were tested using an automatic biochemical analyzer. Liver tissue samples were taken for Masson staining to observe the pathological changes and the degree of liver fibrosis in rats. The protein and mRNA expression of Smad3, Smad4, and TIMP-1 was detected by immunohistochemistry and real-time quantitative PCR (RT-PCR), respectively.

RESULTS: Compared with the model group, the levels of ALT and AST were significantly decreased in the TFL groups. Compared with the normal control group, the extent of fibrosis in the model group increased significantly, and the expression of Smad3, Smad4 and TIMP-1 in liver tissue was significantly enhanced (P < 0.05). Compared with the model group, the expression of Smad3, Smad4 and TIMP-1 showed varying degrees of down-regulation in the TFL groups and colchicine groups.

CONCLUSION: TFL can reduce liver injury and improve liver fibrosis in rats with liver fibrosis, and the underlying mechanism may be closely related with decreasing the expression of Smad3, Smad4 and TIMP-1.

Role of Smad3 in platelet-derived growth factor-C-induced liver fibrosis

Chronic liver injury leads to fibrosis and cirrhosis. Cirrhosis, the end stage of chronic liver disease, is a leading cause of death worldwide and increases the risk of developing hepatocellular carcinoma. Currently, there is a lack of effective antifibrotic therapies to treat fibrosis and cirrhosis. Development of antifibrotic therapies requires an in-depth understanding of the cellular and molecular mechanisms involved in inflammation and fibrosis after hepatic injury. Two growth factor signaling pathways that regulate liver fibrosis are transforming growth factor-β (TGFβ) and platelet-derived growth factor (PDGF). However, their specific contributions to fibrogenesis are not well understood. Using a genetic model of liver fibrosis, we investigated whether the canonical TGFβ signaling pathway was necessary for fibrogenesis. PDGF-C transgenic (PDGF-C Tg) mice were intercrossed with mice that lack Smad3, and molecular and histological fibrosis was analyzed. PDGF-C Tg mice that also lacked Smad3 had less fibrosis and improved liver lobule architecture. Loss of Smad3 also reduced expression of collagen genes, which were induced by PDGF-C, but not the expression of genes frequently associated with hepatic stellate cell (HSC) activation. In vitro HSCs isolated from Smad3-null mice proliferated more slowly than cells from wild-type mice. Taken together, these findings indicate that PDGF-C activates TGFβ/Smad3 signaling pathways to regulate HSC proliferation, collagen production and ultimately fibrosis. In summary, these results suggest that inhibition of both PDGF and TGFβ signaling pathways may be required to effectively attenuate fibrogenesis in patients with chronic liver disease.

The role of motor proteins in signal propagation

The signaling and transport systems of eucaryotic cells are tightly interconnected: intracellular transport along microtubules and microfilaments is required to position signaling-pathway components, while signaling molecules control activity of motor proteins and their interaction with tracks and cargoes. Recent data, however, give evidence that active transport is engaged in signaling as a means of signal transduction. This review focuses on this specific aspect of the interaction of two systems.

Signaling in Fibrosis: TGF-β, WNT, and YAP/TAZ Converge

Chronic organ injury leads to fibrosis and eventually organ failure. Fibrosis is characterized by excessive synthesis, remodeling, and contraction of extracellular matrix produced by myofibroblasts. Myofibroblasts are the key cells in the pathophysiology of fibrotic disorders and their differentiation can be triggered by multiple stimuli. To develop anti-fibrotic therapies, it is of paramount importance to understand the molecular basis of the signaling pathways contributing to the activation and maintenance of myofibroblasts. Several signal transduction pathways, such as transforming growth factor (TGF)-β, Wingless/Int (WNT), and more recently yes-associated protein 1 (YAP)/transcriptional coactivator with PDZ-binding motif (TAZ) signaling, have been linked to the pathophysiology of fibrosis. Activation of the TGF-β1-induced SMAD complex results in the upregulation of genes important for myofibroblast function. Similarly, WNT-stabilized β-catenin translocates to the nucleus and initiates transcription of its target genes. YAP and TAZ are two transcriptional co-activators from the Hippo signaling pathway that also rely on nuclear translocation for their functioning. These three signal transduction pathways have little molecular similarity but do share one principle: the cytosolic/nuclear regulation of its transcriptional activators. Past research on these pathways often focused on the isolated cascades without taking other signaling pathways into account. Recent developments show that parts of these pathways converge into an intricate network that governs the activation and maintenance of the myofibroblast phenotype. In this review, we discuss the current understanding on the signal integration between the TGF-β, WNT, and YAP/TAZ pathways in the development of organ fibrosis. Taking a network-wide view on signal transduction will provide a better understanding on the complex and versatile processes that underlie the pathophysiology of fibrotic disorders.

Signaling in Fibrosis: TGF-β, WNT, and YAP/TAZ Converge

Chronic organ injury leads to fibrosis and eventually organ failure. Fibrosis is characterized by excessive synthesis, remodeling, and contraction of extracellular matrix produced by myofibroblasts. Myofibroblasts are the key cells in the pathophysiology of fibrotic disorders and their differentiation can be triggered by multiple stimuli. To develop anti-fibrotic therapies, it is of paramount importance to understand the molecular basis of the signaling pathways contributing to the activation and maintenance of myofibroblasts. Several signal transduction pathways, such as transforming growth factor (TGF)-β, Wingless/Int (WNT), and more recently yes-associated protein 1 (YAP)/transcriptional coactivator with PDZ-binding motif (TAZ) signaling, have been linked to the pathophysiology of fibrosis. Activation of the TGF-β1-induced SMAD complex results in the upregulation of genes important for myofibroblast function. Similarly, WNT-stabilized β-catenin translocates to the nucleus and initiates transcription of its target genes. YAP and TAZ are two transcriptional co-activators from the Hippo signaling pathway that also rely on nuclear translocation for their functioning. These three signal transduction pathways have little molecular similarity but do share one principle: the cytosolic/nuclear regulation of its transcriptional activators. Past research on these pathways often focused on the isolated cascades without taking other signaling pathways into account. Recent developments show that parts of these pathways converge into an intricate network that governs the activation and maintenance of the myofibroblast phenotype. In this review, we discuss the current understanding on the signal integration between the TGF-β, WNT, and YAP/TAZ pathways in the development of organ fibrosis. Taking a network-wide view on signal transduction will provide a better understanding on the complex and versatile processes that underlie the pathophysiology of fibrotic disorders.

The role of the miR-31/FIH1 pathway in TGF-β-induced liver fibrosis

The miRNAs are small, non-coding RNAs that regulate various biological processes, including liver fibrosis. Hepatic stellate cells (HSCs) play a central role in the pathogenesis of liver fibrosis. By microarray profiling and real-time PCR, we noted that miR-31 expression in HSCs from rats, mice and humans was significantly increased during HSC activation in culture. Overall, miR-31 expression levels were unchanged in the whole-liver RNA extracts from fibrotic rat and human samples. Nevertheless, we found that miR-31 was particularly up-regulated in HSCs but not in hepatocytes during fibrogenesis. Thus, we hypothesized that miR-31 may mediate liver fibrosis. In the present study, we found that inhibition of miR-31 expression significantly inhibited HSC activation, whereas its over-expression obviously promoted HSC activation. Moreover, over-expression of miR-31 promoted HSC migration by enhancing matrix metalloproteinase (MMP)-2 expression whereas inhibition of miR-31 has an opposite effect. The biological function of miR-31 during HSC activation might be through targeting FIH1, a suppressor of hypoxia-inducible factor (HIF-1), because a knockdown of FIH1 by shRNA could mimic the effects of miR-31. In addition, primary rat HSCs were isolated and treated with different cytokines, such as transforming growth factor β (TGF-β), vascular endothelial growth factor and platelet-derived growth factor-BB, to evaluate upstream regulators of miR-31. We found that only TGF-β, a pivotal regulator in liver fibrosis, remarkably increased miR-31 expression in HSCs. And the effects of TGF-β on HSCs can be partially counteracted by inhibition of miR-31. In addition, chromatin immunoprecipitation experiments and the luciferase reporter assay demonstrated that Smad3, a major TGF-β-downstream transcription factor, stimulated the transcription activity of miR-31 by binding directly to miR-31's promoter. In conclusion, the miR-31/FIH1 pathway associates with liver fibrosis, perhaps by participation in the TGF-β/Smad3 signalling of HSCs.

Anti-Fibrotic Effects of Neferine on Carbon Tetrachloride-Induced Hepatic Fibrosis in Mice

The effects of neferine, a bisbenzylisoquinline alkaloid extracted from the seed embryo of the Chinese traditional medicine Nelumbo nucifera Gaertn, on carbon tetrachloride ( CCl 4)-induced hepatic fibrosis in mice were evaluated. Adult male Kunming mice were administered with CCl 4 1 ml/kg via intraperitoneal injection twice a week for 8 weeks. At the beginning of the 9th week, mice were treated with normal saline, colchicine (0.1 mg/kg), and neferine (5, 10, 20 mg/kg) via intraperitoneal injection once a day for 2 weeks. The liver index and histological examination, plasma ALT/AST levels, hydroxyproline and TGF-β1 content of liver tissue were examined. In the model group, the liver index, the hydroxyproline content of liver tissue and plasma ALT/AST levels were increased, and a high expression of TGF-β1 was observed. The abnormal changes could be improved by neferine in a dose-dependent manner. Our data showed that neferine had an antifibrosis effect on CCl 4-induced hepatic fibrosis in mice, possibly partly due to the decreased expression of TGF-β1 in the liver.

Effects of 18α-glycyrrhizin on TGF-β1/Smad signaling pathway in rats with carbon tetrachloride-induced liver fibrosis

BACKGROUND

Glycyrrhizin has various pharmacological effects including hepato-protection. This study aimed to investigate the potential mechanism underlying the protective effects of 18α-glycyrrhizin (18α-GL) in rats with carbon tetrachloride (CCl4) induced liver fibrosis.

METHODS

Male Sprague-Dawley (SD) rats were randomly divided into control group, fibrosis group, 25 mg/kg 18α-GL group and 12.5 mg/kg 18α-GL group. Rats in experimental groups were subcutaneously injected with 40% CCl4 twice weekly for 8 weeks. Immunohistochemical examination was carried out to detect the protein expressions of collagen I, collagen III, TGF-β1, p-Smad2, p-Smad3, Smad 7 and SP-1, in the liver, and the mRNA and protein expressions of these genes were determined in the liver by real time PCR and Western blot assay, respectively.

RESULTS

18α-GL ameliorated histological changes and significantly suppressed collagen deposition. 18α-GL significantly decreased the mRNA expressions of TGF-β1, Smad2, Smad3 and SP-1 in the liver. Immunohistochemical staining revealed that TGF-β1, p-Smad2, p-Smad3 and SP-1 expressions reduced following 18α-GL therapy. Western blot assay showed p-Smad2, p-Smad3, smad2 and smad3 expressions decreased after 18α-GL treatment. The mRNA and protein expression of Smad7 remained unchanged.

CONCLUSION

18α-GL is able to attenuate CCl4 induced liver fibrosis in rat.

Smad2 protects against TGF-β1/Smad3-mediated collagen synthesis in human hepatic stellate cells during hepatic fibrosis

With structural similarity but functional diversity, Smad2 and Smad3 interact with each other to mediate transforming growth factor-β (TGF-β)-triggered signaling transduction. However, in the hepatic fibrosis, the detailed roles of R-Smads, and interaction between Smad2 and Smad3 are still undefined. In this setting, we established a rat model of CCl4-induced hepatic fibrosis in vivo and TGF-β1-treated hepatic stellate cell model in vitro to detect whether Smad2 and Smad3 play distinct roles in mediating liver fibrogenesis. Results indicated that both phosphorylation of Smad2 and Smad3 were detected in the hepatic stellate cells of liver fibrotic tissues and cells. Furthermore, In vitro data demonstrated that knockdown of Smad2 in human hepatic stellate cells increased expression of collagen I (Col.I), tissue inhibitor of metalloproteinase-1 (TIMP-1) whereas decreasing expression of the matrix metalloproteinases-2(MMP-2) in presence of TGF-β1 compared with control group. In contrast, knockdown of Smad3 significantly reduced TGF-β1-induced Col.I production. These findings were further evident by the results that overexpression of Smad2 attenuated the expression of Col.I and TIMP-1, but enhanced MMP-2 whereas overexpression of Smad3 showed the opposite effect. Furthermore, Smad2 suppressed the phosphorylation and nuclear translocation of Smad3, which may protect against Smad3-mediated fibrotic response. Collectively, Smad2 may be a potential therapeutic target for the treatment of hepatic fibrosis.

Hypoxia-sensitive pathways in inflammation-driven fibrosis

Tissue injury can occur for a variety of reasons, including physical damage, infection, and ischemia. The ability of tissues to effectively recover from injury is a cornerstone of human health. The healing response in tissues is conserved across organs and typically involves distinct but overlapping inflammatory, proliferative, and maturation/resolution phases. If the inflammatory phase is not successfully controlled and appropriately resolved, an excessive healing response characterized by scar formation can lead to tissue fibrosis, a major clinical complication in disorders such as Crohn's disease (CD). As a result of enhanced metabolic and inflammatory processes during chronic inflammation, profound changes in tissue oxygen levels occur leading to localized tissue hypoxia. Therefore, inflammation, fibrosis, and hypoxia are coincidental events during inflammation-driven fibrosis. Our current understanding of the mechanism(s) underpinning fibrosis is limited as are the therapeutic options available. In this review, we discuss what is known about the cellular and molecular mechanisms underpinning inflammation-driven fibrosis and how hypoxia may play a role in shaping this process.

Inhibition of acid-sensing ion channel 1a in hepatic stellate cells attenuates PDGF-induced activation of HSCs through MAPK pathway

Acid-sensing ion channels (ASICs), a group of Na(+)-selective and Ca(2+)-permeant ligand-gated cation channels, can be transiently activated by extracellular acid. Among seven subunits of ASICs, acid-sensing ion channel 1a (ASIC1a), which is responsible for Ca(2+) transportation, is elevated in response to inflammation, tumor, and ischemic injury in central nervous system and non-neuronal tissues. In this study, we demonstrated for the first time the presence of ASIC1a in rat liver and hepatic stellate cells (HSCs). Furthermore, the expression of ASIC1a was increased in primary HSCs and liver tissues of CCl4-treated rats, suggesting that ASIC1a may play certain role in liver fibrosis. Interestingly, we identified that the level of ASIC1a was significantly elevated in response to platelet-derived growth factor (PDGF) induction in a time- and dose-dependent manner. It was also established that Ca(2+)-transporting ASIC1a was involved in acid-induced injury of different cell types. Moreover, inhibition or silencing of ASIC1a was able to inhibit PDGF-induced pro-fibrogenic effects of activated rat HSCs, including cell activation, de novo synthesis of extracellular matrix components through mitogen-activated protein kinase signaling pathway. Collectively, our studies identified that ASIC1a was expressed in rat liver and HSCs and provided a strong evidence for the involvement of the ASIC1a in the progression of hepatic fibrosis.

Mechanically and chemically tunable cell culture system for studying the myofibroblast phenotype

Cell culture systems for studying the combined effects of matrix proteins and mechanical forces on the behavior of soft tissue cells have not been well developed. Here, we describe a new biomimetic cell culture system that allows for the study of mixtures of matrix proteins while controlling mechanical stiffness in a range that is physiological for soft tissues. This system consists of layer-by-layer (LbL)-assembled films of native matrix proteins atop mechanically tunable soft supports. We used hepatic stellate cells, which differentiate to myofibroblasts in liver fibrosis, for proof-of-concept studies. By culturing cells on collagen and lumican LbL-modified hydrogels, we demonstrate that this system is noncytotoxic and offers a valid control substrate, that the hydrogel determines the overall system mechanics, and that the addition of lumican to collagen influences the stellate cell phenotype. LbL-modified hydrogels offer the potential to study the influence of complex environmental factors on soft-tissue cells in culture.