Molecular interplays in hepatic stellate cells: apoptosis, senescence, and phenotype reversion as cellular connections that modulate liver fibrosis

Cell senescence in liver diseases: pathological mechanism and theranostic opportunity

The liver is not oblivious to the passage of time, as ageing is a major risk factor for the development of acute and chronic liver diseases. Ageing produces alterations in all hepatic cells, affecting their phenotype and function and worsening the prognosis of liver disease. The ageing process also implies the accumulation of a cellular state characterized by a persistent proliferation arrest and a specific secretory phenotype named cellular senescence. Indeed, senescent cells have key roles in many physiological processes; however, their accumulation owing to ageing or pathological conditions contributes to the damage occurring in chronic diseases. The aim of this Review is to provide an updated description of the pathophysiological events in which hepatic senescent cells are involved and their role in liver disease progression. Finally, we discuss novel geroscience therapies that could be applied to prevent or improve liver diseases and age-mediated hepatic deregulations.

miR-324-3p Suppresses Hepatic Stellate Cell Activation and Hepatic Fibrosis Via Regulating SMAD4 Signaling Pathway

In hepatic fibrosis (HF), hepatic stellate cells (HSCs) form the extracellular matrix (ECM), and the pathological accumulation of ECM in the liver leads to inflammation. Our previous research found that miR-324-3p was down-regulated in culture-activated human HSCs. However, the precise effect of miR-324-3p on HF has not been elucidated. In this study, the HF mouse models were induced through directly injecting carbon tetrachloride (CCl4) into mice; the HF cell models were constructed using TGF-β1-treated LX-2 cells. Next, real-time-quantitative polymerase chain reaction (RT-qPCR), western blot (WB) and immunohistochemistry (IHC) were applied to assess the expression levels of miR-324-3p, α-smooth muscle actin (α-SMA), Vimentin or SMAD4; hematoxylin and eosin (H&E), Masson' s trichrome and Sirius red staining to evaluate the liver injury; luciferase reporter assay to verify the targeting relationship between miR-324-3p and SMAD4; enzyme-linked immunosorbent assay (ELISA) to determine the levels of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST); and cell counting kit-8 (CCK-8) and flow cytometry to evaluate the effects of miR-324-3p on cell proliferation and cycle/apoptosis, respectively. The experimental results showed a reduction in miR-324-3p level in CCl4-induced HF mice as well as transforming growth factor (TGF)-β1-activated HSCs. Interestingly, the miR-324-3p level was rescued following the HF recovery process. In HF mice induced by CCl4, miR-324-3p overexpression inhibited liver tissue damage, decreased serum ALT and AST levels, and inhibited fibrosis-related biomarkers (α-SMA, Vimentin) expression, thereby inhibiting HF. Similarly, miR-324-3p overexpression up-regulated α-SMA and Vimentin levels in HF cells, while knockdown of miR-324-3p had the opposite effect. Besides, miR-324-3p played an antifibrotic role through inhibiting the proliferation of hepatocytes. Further experiments confirmed that miR-324-3p targeted and down-regulated SMAD4 expression. SMAD4 was highly expressed in HF cells, and silencing SMAD4 significantly decreased the α-SMA and Vimentin levels in HF cells. Collectively, the miR-324-3p may suppress the activation of HSCs and HF by targeting SMAD4. Therefore, miR-324-3p is identified as a potential and novel therapeutic target for HF.

In Vitro Lipid Overload Affects Cellular Proliferation, Apoptosis, and Senescence in a Time-Dependent Manner in HepG2 Hepatocytes and LX-2 Hepatic Stellate Cells

Different cellular mechanisms influence steatotic liver disease (SLD) progression. The influence of different levels of steatogenic inputs has not been studied in hepatocytes and hepatic stellate cells (HSCs).

METHODS

HepG2 hepatocytes and LX-2 HSCs were cultured in mild (MS) and severe (SS) steatogenic conditions. TGF-β stimulation was also tested for HSCs in control (T) and steatogenic conditions (MS-T and SS-T). Steatosis was stained with Oil Red, and the proliferation was assayed via WST-8 reduction, apoptosis via flow cytometry, and senescence via SA-β-galactosidase activity.

RESULTS

Regarding hepatocytes, steatosis progressively increased; proliferation was lower in MS and SS; and the viability of both conditions significantly decreased at 72 h. Apoptosis increased in MS at 72 h, while it decreased in SS. Senescence increased in MS and diminished in SS. Regarding HSCs, the SS and SS-T groups showed no proliferation, and the viability was reduced in MS at 72 h and in SS and SS-T. The LX-2 cells showed increased apoptosis in SS and SS-T at 24 h, and in MS and MS-T at 72 h. Senescence decreased in MS, SS, and SS-T.

CONCLUSIONS

Lipid overload induces differential effects depending on the cell type, the steatogenic input level, and the exposure time. Hepatocytes are resilient to mild steatosis but susceptible to high lipotoxicity. HSCs are sensitive to lipid overload, undergoing apoptosis and lowering senescence and proliferation. Collectively, these data may help explain the development of steatosis and fibrosis in SLD.

Placenta mesenchymal stem cell-derived extracellular vesicles alleviate liver fibrosis by inactivating hepatic stellate cells through a miR-378c/SKP2 axis

BACKGROUND

Extracellular vesicles derived from mesenchymal stem/stromal cells (MSCs) have shown therapeutic effects on liver fibrosis. This study aimed to evaluate the effects of extracellular vesicles from placenta-derived MSCs (Pd-MSCs-EVs) on liver fibrosis at 3D/2D levels and explore the potential mechanisms.

METHODS

The multicellular liver organoids, consisting of hepatocytes, hepatic stellate cells (HSCs), Kupffer cells, and liver sinusoidal endothelial cells, were observed for growth status, morphological changes, and metabolism. Human transformation growth factor- beta 1 (TGF-β1) was used to induce fibrosis at optimal concentration. The anti-fibrosis effects of Pd-MSCs-EVs were evaluated in liver organoids and HSCs models. Anti-fibrotic content of Pd-MSCs-EVs was identified by multiple experimental validations.

RESULTS

TGF-β1 induced fibrosis in liver organoids, while Pd-MSCs-EVs significantly alleviated fibrotic phenotypes. Following serial verifications, miR-378c was identified as a potential key anti-fibrosis content. In contrast, miR-378c depletion decreased the anti-fibrotic effects of Pd-MSCs-EVs. Additionally, Pd-MSCs-EVs administration repressed TGF-β1-mediated HSCs activation at 2D or 3D levels. Mechanistically, exosomal miR-378c inactivated HSCs by inhibiting epithelial-mesenchymal transition (EMT) through stabilizing E-cadherin via targeting its E3 ubiquitin ligase S-Phase Kinase Associated Protein 2 (SKP2).

CONCLUSION

Pd-MSCs-EVs ameliorated TGF-β1-induced fibrosis by deactivating HSCs in a miR-378c/SKP2-dependent manner, which may be an efficient therapeutic candidate for liver fibrosis.

Serum response factor activates peroxidasin transcription to block senescence of hepatic stellate cells

AIMS

Aberrant liver fibrosis is a hallmark event in end-stage liver diseases. Hepatic stellate cells (HSCs) are considered the major source of myofibroblasts in the liver that produce extracellular matrix proteins to promote liver fibrosis. HSCs undergo senescence in response to various stimuli, a process that can be exploited to dampen liver fibrosis. We investigated the role of serum response factor (SRF) in this process.

METHODS AND MATERIALS

Senescence was induced HSCs by serum withdrawal or progressive passage. DNA-protein interaction was evaluated by chromatin immunoprecipitation (ChIP).

RESULTS

SRF expression was down-regulated in HSCs entering into senescence. Coincidently, SRF depletion by RNAi accelerated HSC senescence. Of note, treatment of an anti-oxidant (N-acetylcysteine or NAC) blocked HSC senescence by SRF deficiency suggesting that SRF may antagonize HSC senescence by eliminating excessive reactive oxygen species (ROS). PCR-array based screening identified peroxidasin (PXDN) as a potential target for SRF in HSCs. PXDN expression was inversely correlated with HSC senescence whereas PXDN knockdown accelerated HSC senescence. Further analysis reveals that SRF directly bound to the PXDN promoter and activated PXDN transcription. Consistently, PXDN over-expression protected whereas PXDN depletion amplified HSC senescence. Finally, PXDN knockout mice displayed diminished liver fibrosis compared to wild type mice when subjected to bile duct ligation (BDL).

SIGNIFICANCE

Our data suggest that SRF, via its downstream target PXDN, plays a key role in regulating HSC senescence.

The total polyphenolic glycoside extract of Lamiophlomis rotata ameliorates hepatic fibrosis through apoptosis by TGF-β/Smad signaling pathway

BACKGROUND

Hepatic fibrosis is characterized by the excessive deposition of extracellular matrix (ECM) which is mainly secreted by activated hepatic stellate cells (HSCs). Lamiophlomis rotata (L. rotata) was recorded to treat jaundice in the traditional Tibetan medical system with the potential of hepatoprotection. However, the bioactivities and the possible mechanism of L. rotata on hepatic fibrosis is still largely unknown.

AIM OF THE STUDY

To investigate the anti-hepatic fibrosis effects of bioactivities in L. rotata and the probable mechanism of action.

MATERIALS AND METHODS

Herein, total polyphenolic glycosides of L. rotata (TPLR) was purified with the selectivity adsorption resin and was analyzed by ultrahigh-performance liquid chromatography coupled with time-of-flight mass spectrometry (UPLC-Q/TOF/MSⁿ). The anti-hepatic fibrosis effect of TPLR was evaluated by carbon tetrachloride (CCl₄)-induced liver fibrosis, and was evaluated with the apoptosis of activated HSCs.

RESULTS

In total, sixteen compounds, including nine phenylpropanoids and six flavonoids, were identified in the UPLC-TOF-MSⁿ profile of the extracts. TPLR significantly ameliorated hepatic fibrosis in CCl₄-induced mice and inhibited HSCs proliferation, Moreover, TPLR notably increased the apoptosis of activated HSCs along with up-regulated caspase-3, -8, -9, and -10. Furthermore, TPLR inhibited TGF-β/Smad pathway ameliorating hepatic fibrosis though downregulation the expression of Smad2/3, Smad4, and upregulation the expression of Smad7 in vivo and in vitro. Simultaneously, the expression of fibronectin (FN), α-smooth muscle actin (α-SMA), and Collagen I (Col1α1) were decreased in tissues and in cells with TPLR administration.

CONCLUSION

These results initially demonstrated that TPLR has the potential to ameliorate hepatic fibrosis through an apoptosis mechanism via TGF-β/Smad signaling pathway.

Distinct Expression Patterns of Genes Coding for Biological Response Modifiers Involved in Inflammatory Responses and Development of Fibrosis in Chronic Hepatitis C: Upregulation of SMAD-6 and MMP-8 and Downregulation of CAV-1, CTGF, CEBPB, PLG, TIMP-3, MMP-1, ITGA-1, ITGA-2 and LOX

Background and Objectives: The aim of this study was to analyze the expression of genes on transcriptomic levels involved in inflammatory immune responses and the development of fibrosis in patients with chronic hepatitis C. Materials and Methods: Expression patterns of 84 selected genes were analyzed with real-time quantitative RT PCR arrays in the peripheral blood of treatment-naive patients with chronic hepatitis C and healthy controls. The panel included pro- and anti-fibrotic genes, genes coding for extracellular matrix (EMC) structural constituents and remodeling enzymes, cell adhesion molecules, inflammatory cytokines, chemokines and growth factors, signal transduction members of the transforming growth factor- beta (TGF-ß) superfamily, transcription factors, and genes involved in epithelial to mesenchymal transition. Results: The expression of SMAD-6 coding for a signal transduction TGF-beta superfamily member as well as MMP-8 coding for an ECM protein were significantly increased in CHC patients compared with controls. Conclusions: Chronic hepatitis C was also characterized by a significant downregulation of a set of genes including CAV-1, CTGF, TIMP-3, MMP-1, ITGA-1, LOX, ITGA-2, PLG and CEBPB encoding various biological response modifiers and transcription factors. Our results suggest that chronic hepatitis C is associated with distinct patterns of gene expression modulation in pathways associated with the regulation of immune responses and development of fibrosis.

Traditional Chinese medicine: An important source for discovering candidate agents against hepatic fibrosis

Hepatic fibrosis (HF) refers to the pathophysiological process of connective tissue dysplasia in the liver caused by various pathogenic factors. Nowadays, HF is becoming a severe threat to the health of human being. However, the drugs available for treating HF are limited. Currently, increasing natural agents derived from traditional Chinese medicines (TCMs) have been found to be beneficial for HF. A systemic literature search was conducted from PubMed, GeenMedical, Sci-Hub, CNKI, Google Scholar and Baidu Scholar, with the keywords of “traditional Chinese medicine,” “herbal medicine,” “natural agents,” “liver diseases,” and “hepatic fibrosis.” So far, more than 76 natural monomers have been isolated and identified from the TCMs with inhibitory effect on HF, including alkaloids, flavones, quinones, terpenoids, saponins, phenylpropanoids, and polysaccharides, etc. The anti-hepatic fibrosis effects of these compounds include hepatoprotection, inhibition of hepatic stellate cells (HSC) activation, regulation of extracellular matrix (ECM) synthesis & secretion, regulation of autophagy, and antioxidant & anti-inflammation, etc. Natural compounds and extracts from TCMs are promising agents for the prevention and treatment of HF, and this review would be of great significance to development of novel drugs for treating HF.

Targeting the Hepatic Microenvironment to Improve Ischemia/Reperfusion Injury: New Insights into the Immune and Metabolic Compartments

Hepatic ischemia/reperfusion injury (IRI) is mainly characterized by high activation of immune inflammatory responses and metabolic responses. Understanding the molecular and metabolic mechanisms underlying development of hepatic IRI is critical for developing effective therapies for hepatic IRI. Recent advances in research have improved our understanding of the pathogenesis of IRI. During IRI, hepatocyte injury and inflammatory responses are mediated by crosstalk between the immune cells and metabolic components. This crosstalk can be targeted to treat or reverse hepatic IRI. Thus, a deep understanding of hepatic microenvironment, especially the immune and metabolic responses, can reveal new therapeutic opportunities for hepatic IRI. In this review, we describe important cells in the liver microenvironment (especially non-parenchymal cells) that regulate immune inflammatory responses. The role of metabolic components in the diagnosis and prevention of hepatic IRI are discussed. Furthermore, recent updated therapeutic strategies based on the hepatic microenvironment, including immune cells and metabolic components, are highlighted.

MyD88 in hepatic stellate cells promotes the development of alcoholic fatty liver via the AKT pathway

Myeloid differentiation primary response gene 88 (MyD88), an adaptor protein in the Toll-like receptors (TLRs) signalling pathway, is expressed in various liver cells including hepatocytes, Kupffer cells and hepatic stellate cells (HSCs). And yet, the functional role of MyD88 in HSCs is poorly elucidated in alcoholic fatty liver (AFL). Here, to study the functional role of MyD88 in HSCs and the molecular mechanism related to the development of AFL, chronic-binge ethanol mouse models were established in mice with specific MyD88 knockout in quiescent (MyD88^GFAP-KO) and activated HSCs (MyD88^SMA-KO), respectively. Our results clearly showed an elevated expression of MyD88 in liver tissues of ethanol treated mouse model which harbours the wild type. Intriguingly, ethanol treatment profoundly inhibited inflammation in both MyD88^GFAP-KO and MyD88^SMA-KO mice, but the suppression of lipogenesis was only observed in MyD88^GFAP-KO mice. Molecularly, our study indicated that MyD88 induced osteopontin (OPN) secretion in HSCs, which consequently resulted in activation of AKT signalling pathway and accumulation of fat in hepatocytes. Additionally, our data also suggested that OPN promoted inflammation by activating p-STAT1. Thus, targeting MyD88 may be a potentially represent a promising strategy for the prevention and treatment of AFL. KEY MESSAGES: The expression of MyD88 in HSCs was significantly increased in ethanol-induced liver tissues of wild-type mice. MyD88 deficiency in quiescent HSCs inhibited inflammation and lipogenesis under the ethanol feeding condition. MyD88 deficiency in activated HSCs only inhibited inflammation under the ethanol feeding condition. MyD88 promoted the OPN secretion of HSCs, which further activated the AKT signalling pathway of hepatocytes and upregulated lipogenic gene expression to promote fat accumulation. OPN also promotes inflammation by activating p-STAT1.

Definition and classification of acute-on-chronic liver diseases

Patients with chronic liver diseases (CLDs) develop acute liver injury and/or acute decompensation under the attack of various precipitants and present with significantly elevated alanine aminotransferase and/or total bilirubin levels, liver failure, or acute decompensation of liver cirrhosis, which is called acute-on-CLD (AoCLD). AoCLD accounts for the majority of patients hospitalized in the Department of Hepatology or Infectious Diseases. AoCLD is complicated by various clinical types, the severity of the disease, and may pose a high risk of death. To date, the definition of AoCLD is still vague, and a consensus concept of the clinical classification is lacking. This review aimed to define the concept and clinical types of AoCLD based on related studies and the literature.

Mannan-Binding Lectin via Interaction With Cell Surface Calreticulin Promotes Senescence of Activated Hepatic Stellate Cells to Limit Liver Fibrosis Progression

BACKGROUND & AIMS

Liver fibrosis represents a hallmark of most chronic liver diseases (CLD) triggered by recurrent liver injury and subsequent myofibroblast transdifferentiations of resident hepatic stellate cells (HSCs). Mannan-binding lectin (MBL) is potentially involved in hepatic fibrosis in CLD through unclear mechanisms. Therefore, we investigated the crosstalk between MBL and HSCs, and the consequent effects on fibrosis progression.

METHODS

Samples from patients with liver cirrhosis were collected. MBL deficiency (MBL^-/-) and wild-type (WT) C57BL/6J mice were used to construct a CCl₄-induced liver fibrosis model. Administration of MBL-expressing, liver-specific, adeno-associated virus was performed to restore hepatic MBL expression in MBL^-/- mice. The human HSC line LX-2 was used for in vitro experiments.

RESULTS

MBL levels in patients with liver cirrhosis were correlated with disease severity. In the CCl4-induced liver fibrosis model, MBL^-/- mice showed severer liver fibrosis accompanied by reduced senescent activated HSCs in liver tissue compared with WT mice, which could be inhibited by administering MBL-expressing, liver-specific, adeno-associated virus. Moreover, depleting senescent cells with senolytic treatment could abrogate these differences owing to MBL absence. Furthermore, MBL could interact directly with calreticulin associated with low-density lipoprotein receptor-related protein 1 on the cell surface of HSCs, which further promotes senescence in HSCs by up-regulating the mammalian target of rapamycin/p53/p21 signaling pathway.

CONCLUSIONS

MBL as a newfound senescence-promoting modulator and its crosstalk with HSCs in the liver microenvironment is essential for the control of hepatic fibrosis progression, suggesting its potential therapeutic use in treating CLD associated with liver fibrosis.

Calcipotriol attenuates liver fibrosis through the inhibition of vitamin D receptor-mediated NF-κB signaling pathway

Liver fibrosis is an inevitable stage in the development of chronic liver disease to cirrhosis. Nonetheless, the interventional treatment and achieving control over the disease at this stage can substantially reduce the incidence of liver cirrhosis. To demonstrate these aspects, liver pathological sections of 18 patients with chronic liver disease are collected for research according to the degree of fibrosis. Further, the expressions of related proteins in each group are studied by the Western blot method. The cell proliferation and apoptosis are detected by CKK-8 and flow cytometry analyses. Further, a rat model with carbon tetrachloride (CCl₄)-induced liver fibrosis is employed to verify the effect and mechanism of VDR on the process of liver fibrosis in vivo. The expression of VDR in liver tissues of patients with liver fibrosis is negatively correlated with α-smooth muscle actin (α-SMA), Col-1, and liver fibrosis stages. Moreover, the tumor necrosis factor (TNF)-α stimulation could increase the proliferation of LX-2, up-regulate the expression of α-SMA, Col-1, NF-κB, p-IκBα, p-IKKβ, p-p65m, and some fibrosis factors, as well as down-regulate the expressions of VDR and matrix metalloproteinase-1 (MMP-1). Considering the protective actions of VDR, calcipotriol, a VDR agonist, effectively reduced the degree of liver fibrosis in a rat model of liver fibrosis by inhibiting the deposition of extracellular (ECM) and activation of hepatic stellate cells (HSCs), which is negatively correlated with the degree of liver fibrosis. Together, these shreds of evidence demonstrated that the calcipotriol showed great potential in effectively attenuating liver fibrosis.

Effect of Candesartan and Ramipril on Liver Fibrosis in Patients with Chronic Hepatitis C Viral Infection: A Randomized Controlled Prospective Study

Objective: This study aimed at evaluating the effects of candesartan and ramipril on liver fibrosis in patients with chronic hepatitis C. Methods: This randomized controlled prospective study involved 64 patients with chronic hepatitis C and liver fibrosis. Participants were randomized into 3 groups: group I (control group; n = 21), members of which received traditional therapy only; group 2 (ramipril group; n = 21), members of which received traditional therapy plus 1.25 mg/d oral ramipril; and group 3 (candesartan group; n = 22), members of which received traditional therapy plus 8 mg/d oral candesartan. Patients were assessed at baseline and 6 months after intervention through measuring of liver stiffness (Fibro-Scan; Echosens, Paris, France); evaluation of the serum levels of hyaluronic acid and transforming growth factor beta-1; and calculation of indices of liver fibrosis, including fibrosis index based on the 4 factors and aspartate transaminase-to-platelet-ratio index. Data were analyzed using paired t test and 1-way ANOVA followed by Tukey's honest significant difference test for multiple pairwise comparisons. Results: At baseline, the 3 study groups were statistically similar in demographic and laboratory data. After treatment, the 3 study groups showed significant decrease in liver stiffness, serum levels of hyaluronic acid and transforming growth factor beta-1, and indices of liver fibrosis compared with baseline data (P < 0.001). Six months after treatment, patients taking ramipril and candesartan showed significant improvement in all measured parameters compared with the control group. Additionally, the candesartan-treated group showed significant decrease in liver stiffness, biomarkers, and indices of liver fibrosis compared with ramipril recipients. Conclusions: The administration of ramipril and candesartan in patients with chronic hepatitis C with hepatic fibrosis was well tolerated and effective in improving liver fibrosis. angiotensin II receptor 1 (AT1) antagonist candesartan maintained antifibrotic effects more effectively than ramipril and may represent a safe and effective therapeutic strategy for liver fibrosis in patients with chronic liver diseases. ClinicalTrials.gov identifier: NCT03770936. (Curr Ther Res Clin Exp. 2022; 83:XXX-XXX) © 2022 Elsevier HS Journals, Inc.

Therapeutic Effects of an Inhibitor of Thioredoxin Reductase on Liver Fibrosis by Inhibiting the Transforming Growth Factor-β1/Smads Pathway

Liver fibrosis is an important stage in the progression of liver injury into cirrhosis or even liver cancer. Hepatic stellate cells (HSCs) are induced by transforming growth factor-β1 (TGF-β1) to produce α-smooth muscle actin (α-SMA) and collagens in liver fibrosis. Butaselen (BS), which was previously synthesized by our group, is an organic selenium compound that exerts antioxidant and tumor cell apoptosis–promoting effects by inhibiting the thioredoxin (Trx)/thioredoxin reductase (TrxR) system. The aim of this study was to investigate the potential effects of BS on liver fibrosis and explore the underlying molecular mechanisms of its action. Liver fibrosis models were established using male BALB/c mice through intraperitoneal injection of CCl₄. BS was administered orally once daily at a dose of 36, 90, or 180 mg/kg. Silymarin (Si), which is a drug used for patients with nonalcoholic fatty liver disease and nonalcoholic steatohepatitis, was administered at a dose of 30 mg/kg per day as a control. The action mechanisms of BS against liver fibrosis progression were examined in HSCs. The study revealed that the activity and expression levels of TrxR were elevated in the mouse liver and serum after CCl₄-induced liver fibrosis. Oral administration of BS relieved the pathological state of mice with liver fibrosis, showing significant therapeutic effects against liver fibrosis. Moreover, BS not only induced HSC apoptosis but also inhibited the production of α-SMA and collagens by HSCs by downregulating the TGF-β1 expression and blocking the TGF-β1/Smads pathway. The results of the study indicated that BS inhibited liver fibrosis by regulating the TGF-β1/Smads pathway.

Thioacetamide-induced norepinephrine production by hepatocytes is associated with hepatic stellate cell activation and liver fibrosis

BACKGROUND

Collagen production by activated hepatic stellate cells (HSCs) to encapsulate injury is part of the natural wound-healing response in injured liver. However, persistent activation of HSCs can lead to pathological fibrogenesis. Such persistent HSC activation could be mediated by norepinephrine (NE), a reaction product of dopamine beta-hydroxylase (DBH).

OBJECTIVE

To investigate the potential paracrine role of NE in hepatotoxin thioacetamide (TAA)-induced liver fibrosis.

METHODS/RESULTS

In TAA-treated mice, fibrotic liver tissue showed significant increases in the mRNA expression of DBH up to 14-fold and collagen up to 7-fold. Immunohistochemical staining showed increased DBH protein expression in fibrotic liver tissue. Parenchymal hepatocyte cell line HepG2 expressed DBH and secreted NE, and the conditioned medium of HepG2 cells promoted collagenesis in nonparenchymal HSC cell line LX-2. TAA treatment increased DBH expression by 170% in HepG2 cells, as well as increased NE by 120% in the conditioned medium of HepG2 cells. The conditioned medium of TAA-treated HepG2 cells was used to culture LX-2 cells, and was found to increase collagen expression by 80% in LX-2 cells. Collagen expression was reduced by pre-treating HepG2 cells with siRNA targeting DBH or by adding NE antagonists to the conditioned medium. Finally, TAA-induced oxidative stress in HepG2 cells was associated with induction of DBH expression.

CONCLUSION

Collectively, our results suggest a potential role for DBH/NE-mediated crosstalk between hepatocytes and HSCs in fibrogenesis. From a therapeutic standpoint, antagonism of DBH/NE induction in hepatocytes might be a useful strategy to suppress pathological fibrogenesis.

STAT3 Promotes Schistosome-Induced Liver Injury by Inflammation, Oxidative Stress, Proliferation, and Apoptosis Signal Pathway

Schistosomiasis is a parasitic helminth disease that can cause organ lesions leading to health damage. During a schistosome infection, schistosome eggs can flow into the liver along the portal vein. Numerous inflammatory cells gather around the eggs, causing granulomas and fibrosis in the liver. In this process, many molecules are involved in the initiation and regulation of the fibrous scar formation. However, the precise molecular mechanisms responsible for the progression of granuloma formation and fibrosis initiation caused by schistosome infection have not been extensively studied. In this study, C57BL/6 wild-type mice and Stat3^flox/flox Alb-Cre mice were infected with cercariae of Schistosoma japonicum Liver injury, effector molecule levels, and RNA transcriptome resequencing of liver tissue were detected at 4, 5, and 6 weeks postinfection. We investigated the role of STAT3 (signal transducer and activator of transcription 3) in Schistosoma-induced liver injury in mice. After 6 weeks postinfection, there was obvious liver fibrosis. A sustained pathological process (inflammation, oxidative stress, proliferation, and apoptosis) occurred in S. japonicum-induced liver fibrosis initiation. Meanwhile, we observed activation of the STAT3 pathway in hepatic injury during S. japonicum infection by RNA transcriptome resequencing. Liver deficiency of phospho-STAT3 alleviated infection-induced liver dysfunction, hepatic granuloma formation, and fibrosis initiation. It also promoted STAT3-dependent apoptosis and reduced liver inflammation, oxidative stress, and proliferation. Our results suggest that STAT3 signal pathway and its mediating inflammation, oxidative stress, proliferation, and apoptosis are involved in S. japonicum-induced liver injury and may be a new potential guideline for the treatment of schistosomiasis.

Selonsertib Inhibits Liver Fibrosis via Downregulation of ASK1/ MAPK Pathway of Hepatic Stellate Cells

Liver fibrosis constitutes a significant health problem worldwide due to its rapidly increasing prevalence and the absence of specific and effective treatments. Growing evidence suggests that apoptosis-signal regulating kinase 1 (ASK1) is activated in oxidative stress, which causes hepatic inflammation and apoptosis, leading to liver fibrogenesis through a mitogen-activated protein kinase (MAPK) downstream signals. In this study, we investigated whether selonsertib, a selective inhibitor of ASK1, shows therapeutic efficacy for liver fibrosis, and elucidated its mechanism of action in vivo and in vitro. As a result, selonsertib strongly suppressed the growth and proliferation of hepatic stellate cells (HSCs) and induced apoptosis by increasing Annexin V and TUNEL-positive cells. We also observed that selonsertib inhibited the ASK1/MAPK pathway, including p38 and c-Jun N-terminal kinase (JNK) in HSCs. Interestingly, dimethylnitrosamine (DMN)-induced liver fibrosis was significantly alleviated by selonsertib treatment in rats. Furthermore, selonsertib reduced collagen deposition and the expression of extracellular components such as α-smooth muscle actin (α-SMA), fibronectin, and collagen type I in vitro and in vivo. Taken together, selonsertib suppressed fibrotic response such as HSC proliferation and extracellular matrix components by blocking the ASK1/MAPK pathway. Therefore, we suggest that selonsertib may be an effective therapeutic drug for ameliorating liver fibrosis.

miR-125b acts as anti-fibrotic therapeutic target through regulating Gli3 in vivo and in vitro

INTRODUCTION AND OBJECTIVES

Liver fibrosis is a major characteristic of most chronic liver diseases which leads to accumulation of extracellular matrix (ECM) proteins. Hedgehog (Hh) pathway activated by Gli genes participated in the pathogenesis of liver fibrosis. However, the regulatory role of miR-125b in liver fibrosis via targeting Gli genes remains unknown.

MATERIALS AND METHODS

RT-qPCR and western blot were employed to the expression levels of mRNA and protein, respectively. The fibrosis level of liver tissue was determined by Masson's trichrome staining. The interaction between miR-125b and Gli3 was tested by luciferase reporter assay. In addition, LX2 cells were activated and CCl₄-induced rat model was used in this study.

RESULTS

miR-125b was significantly declined in serum samples of the clinical liver fibrosis patient, activated LX2 cells and the liver tissues of the CCl₄-induced rat model. Furthermore, in cellular level, the alpha-smooth muscle actin (α-SMA) and Albumin expressions were ascending and descending in LX2 cells, respectively, with the decline of miR-125b. However, when transfecting with miR-125b mimic, the expressions of α-SMA and Albumin was reversed and Gli3 expression was notably repressed in LX2 cells. The target interaction between miR-125b and Gli3 was determined by dual-luciferase assays. It was further discovered that the changes of α-SMA, Albumin, and Gli3 were similar to the expression trend in LX2 cells with miR-125b mimic transfection.

CONCLUSION

These results suggested that miR-125b might be protective against liver fibrosis via regulating Gli3 and it might be a promising target in the development of novel therapies to treat pathological fibrotic disorders.

Prophylactical Low Dose Whole-Liver Irradiation Inhibited Colorectal Liver Metastasis by Regulating Hepatic Niche in Mice

Background

The liver is the most common target for metastatic colorectal cancer. Changes of the local hepatic niche due to hepatic diseases such as cirrhosis decrease the incidence of colorectal cancer liver metastasis. Hepatic niche heterogeneity could influence the risk of hepatic metastasis.

Materials and Methods

We simulated changes of the hepatic niche via prophylactical liver irradiation with a safe dose of 6 Gy. GEO dataset and GO analysis revealed a difference in the expression of matrix metalloproteinase 1 (MMP1) in primary colorectal cancer versus liver metastasis, as well as synchronous versus metachronous liver metastasis. Western blotting, Immunofluorescence and qRT-PCR were conducted to measure protein expressions, location and RNA expressions. Colony formation, wound-healing, transwell assays experiments were performed to determine the malignant biological properties of colorectal cancer cells. shRNA transfection was used to conduct stable transfected cell lines.

Results

Tissue inhibitor of metalloproteinases 1 (TIMP1) expression was significantly higher in metastases lesions than primary tumors. In vivo, TIMP1 expression in the hepatic niche increased after a safe dose of 6 Gy irradiation, along with MMP1 decreased, leading to collagen fiber deposition and impairment of hepatic microcirculation. In vitro, irradiated hepatic stellate cells-conditioned media reduced the migration and clone formation ability of colon cancer cells SW480 and HCT116. Low TIMP1 expression in hepatic stellate cells reduced tumor cell invasion and migration.

Conclusion

Prophylactical 6 Gy whole-liver irradiation could inhibit colorectal cancer liver metastasis by regulating TIMP1/MMP1 balance in the hepatic niche before liver metastatic lesion formed.

PLK1 regulates hepatic stellate cell activation and liver fibrosis through Wnt/β-catenin signalling pathway

As an outcome of chronic liver disease, liver fibrosis involves the activation of hepatic stellate cells (HSCs) caused by a variety of chronic liver injuries. It is important to explore approaches to inhibit the activation and proliferation of HSCs for the treatment of liver fibrosis. PLK1 is overexpressed in many human tumour cells and has become a popular drug target in tumour therapy. Therefore, further study of the function of PLK1 in the cell cycle is valid. In the present study, we found that PLK1 expression was elevated in primary HSCs isolated from CCl4 -induced liver fibrosis mice and LX-2 cells stimulated with TGF-β1. Knockdown of PLK1 inhibited α-SMA and Col1α1 expression and reduced the activation of HSCs in CCl4 -induced liver fibrosis mice and LX-2 cells stimulated with TGF-β1. We further showed that inhibiting the expression of PLK1 reduced the proliferation of HSCs and promoted HSCs apoptosis in vivo and in vitro. Furthermore, we found that the Wnt/β-catenin signalling pathway may be essential for PLK1-mediated HSCs activation. Together, blocking PLK1 effectively suppressed liver fibrosis by inhibiting HSC activation, which may provide a new treatment strategy for liver fibrosis.

Relevance of SIRT1-NF-κB Axis as Therapeutic Target to Ameliorate Inflammation in Liver Disease

Inflammation is an adaptive response in pursuit of homeostasis reestablishment triggered by harmful conditions or stimuli, such as an infection or tissue damage. Liver diseases cause approximately 2 million deaths per year worldwide and hepatic inflammation is a common factor to all of them, being the main driver of hepatic tissue damage and causing progression from non-alcoholic fatty liver disease (NAFLD) to non-alcoholic steatohepatitis (NASH), cirrhosis and, ultimately, hepatocellular carcinoma (HCC). The metabolic sensor SIRT1, a class III histone deacetylase with strong expression in metabolic tissues such as the liver, and transcription factor NF-κB, a master regulator of inflammatory response, show an antagonistic relationship in controlling inflammation. For this reason, SIRT1 targeting is emerging as a potential strategy to improve different metabolic and/or inflammatory pathologies. In this review, we explore diverse upstream regulators and some natural/synthetic activators of SIRT1 as possible therapeutic treatment for liver diseases.

Dynamic Changes in Function and Proteomic Composition of Extracellular Vesicles from Hepatic Stellate Cells during Cellular Activation

During chronic liver injury, hepatic stellate cells (HSC) undergo activation and are the principal cellular source of collagenous scar. In this study, we found that activation of mouse HSC (mHSC) was associated with a 4.5-fold increase in extracellular vesicle (EV) production and that fibrogenic gene expression (CCN2, Col1a1) was suppressed in Passage 1 (P1; activated) mHSC exposed to EVs from Day 4 (D4; relatively quiescent) mHSC but not to EVs from P1 mHSC. Conversely, gene expression (CCN2, Col1a1, αSMA) in D4 mHSC was stimulated by EVs from P1 mHSC but not by EVs from D4 mHSC. EVs from Day 4 mHSC contained only 46 proteins in which histones and keratins predominated, while EVs from P1 mHSC contained 337 proteins and these were principally associated with extracellular spaces or matrix, proteasome, collagens, vesicular transport, metabolic enzymes, ribosomes and chaperones. EVs from the activated LX-2 human HSC (hHSC) line also promoted fibrogenic gene expression in D4 mHSC in vitro and contained 524 proteins, many of which shared identity or had functional overlap with those in P1 mHSC EVs. The activation-associated changes in production, function and protein content of EVs from HSC likely contribute to the regulation of HSC function in vivo and to the fine-tuning of fibrogenic pathways in the liver.

Toll-Like Receptor 5 Signaling Ameliorates Liver Fibrosis by Inducing Interferon β-Modulated IL-1 Receptor Antagonist in Mice

Bacterial flagellin, recognized by cell surface of Toll-like receptor (TLR) 5, is a potent activator of many types of cells, leading to the activation of innate or adaptive immunity, which are pivotal in regulating fibrotic process. However, the exact role of TLR5 signaling in hepatic fibrogenesis remains unclear, and this study aims to elucidate its underlying mechanisms. Flagellin was injected to hepatotoxin- and cholestasis-induced liver fibrosis murine models. Flagellin-induced TLR5 activation significantly decreased the severity of liver fibrosis. Interestingly, the expression levels of IL-1 receptor antagonist (IL1RN) and interferon (IFN)β markedly increased in fibrotic livers on flagellin treatment. Consistently, in vivo activation of TLR5 signaling markedly increased IFNβ and IL1RN expression in the livers. Notably, flagellin injection significantly exacerbated the severity of liver fibrosis in IFN-α/β receptor 1 (IFNAR1) knockout mice. Furthermore, hepatic expression of IL1RN in the fibrotic livers of IFNAR1 knockout mice was significantly lower than those of wild-type mice. In support of these findings, flagellin-mediated IL1RN production is not sufficient to alleviate the severity of hepatic fibroinflammatory responses in IFNAR1-deficient milieu. Finally, hepatic stellate cells treated with IL1RN had significantly decreased cellular activation and its associated fibrogenic responses. Collectively, manipulation of TLR5 signaling may be a promising therapeutic strategy for the treatment of liver fibrosis.

Astragaloside IV regulates NF-κB-mediated cellular senescence and apoptosis of hepatic stellate cells to suppress PDGF-BB-induced activation

Activated hepatic stellate cells (HSCs) are the principal effectors during hepatic fibrosis, which is characterized by the accumulation of extracellular matrix. Therefore, present therapies and investigations into hepatic fibrosis mainly focus on the suppression of activated HSCs. Astragaloside IV (ASIV) is an effective constituent extracted from the plant Astragalus membranaceus and has exhibited anti-fibrotic properties in hepatic fibrosis. However, its protective mechanism against hepatic fibrosis is not fully understood. The present study aimed to investigate the mechanistic role of ASIV on rat HSC-T6 cells activated with platelet-derived growth factor (PDGF)-BB. HSC-T6 cells were activated using PDGF-BB and subsequently treated with ASIV (final concentrations of 20 and 40 µg/ml) for 48 h. ASIV treatment decreased the expression of α1 type I collagen, α-smooth muscle actin and fibronectin on mRNA and protein levels, suggesting that ASIV suppresses PDGF-BB-induced HSC-T6 activation. Senescence-associated β-galactosidase activity, p21, high-mobility group AT-hook 1 and p53, common biomarkers of senescence, were upregulated by ASIV treatment. In addition, the expression of telomerase reverse transcriptase was reduced. ASIV promoted apoptosis of PDGF-BB-activated HSC-T6 cells. The NF-κB signaling pathway, which controls cellular senescence and apoptosis, was demonstrated to be stimulated by ASIV by increasing p65, p52, p50 and inhibitor of NF-κB kinase α expression levels, and by suppressing the expression of NF-κB inhibitor α. Taken together, these results demonstrated that ASIV promoted cellular senescence and apoptosis by activating the NF-κB pathway to suppress PDGF-BB-induced HSC-T6 activation; with potential implications for the treatment of hepatic fibrosis.

miR-140-3p Knockdown Suppresses Cell Proliferation and Fibrogenesis in Hepatic Stellate Cells via PTEN-Mediated AKT/mTOR Signaling

PURPOSE

Liver fibrosis is a major cause of morbidity and mortality and the outcome of various chronic liver diseases. Activation of hepatic stellate cells (HSCs) is the key event in liver fibrosis. Studies have confirmed that miR-140-3p plays a potential regulatory effect on HSC activation. However, whether miR-140-3p mediates the liver fibrosis remains unknown.

MATERIALS AND METHODS

Expression of miR-140-3p was detected by real-time quantitative PCR (qPCR). Cell proliferation was measured by MTT, while cell apoptosis rate was determined via flow cytometry. Western blot assay was used to detect the expression of cleaved PARP. The fibrogenic effect was evaluated by expression of α-smooth muscle actin and desmin. Functional experiments were performed in transforming growth factor β1 (TGF-β1)-induced HSC-T6 cells with transfection of anti-miR-140-3p and/or siPTEN. Target binding between miR-140-3p and PTEN was predicted by the TargetScan database and identified using luciferase reporter assay and RNA immunoprecipitation.

RESULTS

TGF-β1 induced the activation of HSC-T6 cells, and miR-140-3p expression varied according to HSC-T6 cell activation status. Knockdown of miR-140-3p reduced cell proliferation and the expressions of α-SMA and desmin, as well as increased apoptosis, in TGF-β1-induced HSC-T6 cells, which could be blocked by PTEN silencing. Additionally, inactivation of the AKT/mTOR signaling pathway stimulated by miR-140-3p knockdown was abolished when silencing PTEN expression. PTEN was negatively regulated by miR-140-3p via direct binding in HSC-T6 cells.

CONCLUSION

miR-140-3p is an important mediator in HSC-T6 cell activation, and miR-140-3p knockdown suppresses cell proliferation and fibrogenesis in TGF-β1-induced HSC-T6 cells, indicating that miR-140-3p may be a potential novel molecular target for liver fibrosis.

Role of Metabolism in Hepatic Stellate Cell Activation and Fibrogenesis

Activation of hepatic stellate cell (HSC) involves the transition from a quiescent to a proliferative, migratory, and fibrogenic phenotype (i.e., myofibroblast), which is characteristic of liver fibrogenesis. Multiple cellular and molecular signals which contribute to HSC activation have been identified. This review specially focuses on the metabolic changes which impact on HSC activation and fibrogenesis.

P53-dependent induction of ferroptosis is required for artemether to alleviate carbon tetrachloride-induced liver fibrosis and hepatic stellate cell activation

Ferroptosis is recently reported as a new mode of regulated cell death. Its essential characteristics are disturbed redox homeostasis, overloaded iron, and increased lipid peroxidation. However, the role of ferroptosis in liver fibrosis remains poorly understood. In this study, we attempted to investigate the effect of artemether (ART) on ferroptosis in hepatic fibrosis and to further clarify the possible mechanisms. Our data showed that ART treatment markedly attenuated liver injury and reduced fibrotic scar formation in the mouse model of liver fibrosis. Moreover, experiments in vitro also confirmed that ART treatment significantly decreased expression of hepatic stellate cell (HSC) activation markers. Interestingly, HSCs treated by ART presented morphological features of ferroptosis. Furthermore, ART remarkably triggered ferroptosis by promoting the accumulation of iron and lipid peroxides, whereas inhibition of ferroptosis by specific inhibitor ferrostatin-1 (Fer-1) completely abolished ART-induced antifibrosis effect. More importantly, our discovery determined that tumor suppressor P53 was an upstream molecule in the facilitation of ART-induced HSC ferroptosis. Conversely, knockdown of P53 by siRNA evidently blocked ART-induced HSC ferroptosis in turn exacerbated liver fibrosis. Overall, our findings revealed that P53-dependent induction of ferroptosis is necessary for ART to ameliorate CCl₄ -induced hepatic fibrosis and inhibit HSC activation. © 2018 IUBMB Life, 71(1):45-56, 2019.

Emodin suppresses activation of hepatic stellate cells through p38 mitogen-activated protein kinase and Smad signaling pathways in vitro

The aim of this study was to evaluate the hypothesis that emodin inhibits extracellular matrix (ECM)-related gene expression in activated hepatic stellate cells (HSCs) by blocking canonical or/and noncanonical components of transforming growth factor β1 (TGFβ1) intracellular signaling. Here, we demonstrate that emodin suppressed the gene expression of HSCs activation markers type I collagen, fibronectin, and α-smooth muscle actin, as well as HSCs proliferation. Mechanistically, emodin suppresses TGFβ1, TGFβ receptor II, TGFβ receptor I, and Smad4 gene expression, as well as Smad luciferase activity. Simultaneously, emodin reduced p38 mitogen-activated protein kinase (p38^MAPK ) activity but not c-Jun N-terminal kinases and extracellular signal-regulated kinases 1 and 2 phosphorylation in HSC-T6 cells. Interestingly, deprivation of TGFβ using a neutralizing antibody abolished emodin-mediated inhibitions of the both Smad transcriptional activity and p38^MAPK phosphorylation. Furthermore, emodin-mediated inhibition of HSCs activation could be partially blocked by PD98059 inhibition of p38^MAPK or short hairpin RNA-imposed knockdown of Smad4. Conversely, simultaneous inhibition of Smad4 and p38^MAPK pathways completely reverses the effects of emodin, suggesting that Smad and p38^MAPK locate downstream of TGFβ1 and regulate collagen genes expression in HSCs. Collectively, these data suggest that emodin is a promising candidate for the treatment of hepatic fibrosis.

Characterization of Pattern Recognition Receptor Expression and Functionality in Liver Primary Cells and Derived Cell Lines

Different liver cell types are endowed with immunological properties, including cell-intrinsic innate immune functions that are important to initially control pathogen infections. However, a full landscape of expression and functionality of the innate immune signaling pathways in the major human liver cells is still missing. In order to comparatively characterize these pathways, we purified primary human hepatocytes, hepatic stellate cells, liver sinusoidal endothelial cells (LSEC), and Kupffer cells (KC) from human liver resections. We assessed mRNA and protein expression level of the major innate immune sensors, as well as checkpoint-inhibitor ligands in the purified cells, and found Toll-like receptors (TLR), RIG-I-like receptors, as well as several DNA cytosolic sensors to be expressed in the liver microenvironment. Amongst the cells tested, KC were shown to be most broadly active upon stimulation with PRR ligands emphasizing their predominant role in innate immune sensing the liver microenvironment. By KC immortalization, we generated a cell line that retained higher innate immune functionality as compared to THP1 cells, which are routinely used to study monocyte/macrophages functions. Our findings and the establishment of the KC line will help to understand immune mechanisms behind antiviral effects of TLR agonists or checkpoint inhibitors, which are in current preclinical or clinical development.

p300/CBP as a Key Nutritional Sensor for Hepatic Energy Homeostasis and Liver Fibrosis

The overwhelming frequency of metabolic diseases such as obesity and diabetes are closely related to liver diseases, which might share common pathogenic signaling processes. These metabolic disorders in the presence of inflammatory response seem to be triggered by and to reside in the liver, which is the central metabolic organ that plays primary roles in regulating lipid and glucose homeostasis upon alterations of metabolic conditions. Recently, abundant emerging researches suggested that p300 and CREB binding protein (CBP) are crucial regulators of energy homeostasis and liver fibrosis through both their acetyltransferase activities and transcriptional coactivators. Plenty of recent findings demonstrated the potential roles of p300/CBP in mammalian metabolic homeostasis in response to nutrients. This review is focused on the different targets and functions of p300/CBP in physiological and pathological processes, including lipogenesis, lipid export, gluconeogenesis, and liver fibrosis, also provided some nutrients as the regulator of p300/CBP for nutritional therapeutic approaches to treat liver diseases.

Novel Insights on Notch signaling pathways in liver fibrosis

Liver fibrosis is characterized by an increased and altered deposition of extracellular matrix (ECM) proteins that make up excessive tissue scarring and promote chronic liver injury. Activation of hepatic stellate cells (HSCs) is a pivotal cellular event in the progression of liver fibrosis. However, the mechanisms involved in the development of liver fibrosis are only now beginning to be unveiled. The Notch pathway is a fundamental and highly conserved pathway able to control cell-fate, including cell proliferation, differentiation, apoptosis, regeneration and other cellular activities. Recently, the deregulation of Notch cascade has been found involved in many pathological processes, including liver fibrosis. These data give evidence for a role for Notch signaling in liver fibrosis. In addition，more and more date are available on the role of Notch pathways in the process. Therefore, this review focuses on the current knowledge about the Notch signaling pathway, which dramatically takes part in HSC activation and liver fibrosis, and look ahead on new perspectives of Notch signaling pathway research. Furthermore, we will summarize this new evidence on the different interactions in Notch signaling pathway-regulated liver fibrosis, and support the potentiality of putative biomarkers and unique therapeutic targets.

"Thinking" vs. "Talking": Differential Autocrine Inflammatory Networks in Isolated Primary Hepatic Stellate Cells and Hepatocytes under Hypoxic Stress

We hypothesized that isolated primary mouse hepatic stellate cells (HSC) and hepatocytes (HC) would elaborate different inflammatory responses to hypoxia with or without reoxygenation. We further hypothesized that intracellular information processing (“thinking”) differs from extracellular information transfer (“talking”) in each of these two liver cell types. Finally, we hypothesized that the complexity of these autocrine responses might only be defined in the absence of other non-parenchymal cells or trafficking leukocytes. Accordingly, we assayed 19 inflammatory mediators in the cell culture media (CCM) and whole cell lysates (WCLs) of HSC and HC during hypoxia with and without reoxygenation. We applied a unique set of statistical and data-driven modeling techniques including Two-Way ANOVA, hierarchical clustering, Principal Component Analysis (PCA) and Network Analysis to define the inflammatory responses of these isolated cells to stress. HSC, under hypoxic and reoxygenation stresses, both expressed and secreted larger quantities of nearly all inflammatory mediators as compared to HC. These differential responses allowed for segregation of HSC from HC by hierarchical clustering. PCA suggested, and network analysis supported, the hypothesis that above a certain threshold of cellular stress, the inflammatory response becomes focused on a limited number of functions in both HSC and HC, but with distinct characteristics in each cell type. Network analysis of separate extracellular and intracellular inflammatory responses, as well as analysis of the combined data, also suggested the presence of more complex inflammatory “talking” (but not “thinking”) networks in HSC than in HC. This combined network analysis also suggested an interplay between intracellular and extracellular mediators in HSC under more conditions than that observed in HC, though both cell types exhibited a qualitatively similar phenotype under hypoxia/reoxygenation. Our results thus suggest that a stepwise series of computational and statistical analyses may help decipher how cells respond to environmental stresses, both within the cell and in its secretory products, even in the absence of cooperation from other cells in the liver.

SENP1 attenuates the liver fibrosis through down-regulating the expression of SMAD2

To investigate whether SENP1 could play a regulating role in the liver fibrosis process, the Sprague-Dawley (SD) rats were used to establish the liver fibrosis rat models by intraperitoneally injecting with 1 ml/kg of 10% CCl₄, while the control normal rats were injected with olive oil. Then confirmation experiments to verify the successful establishment of these models were conducted by detecting the cellular and lobular architecture, and liver function indexes using hematoxylin-eosin staining, Masson's trichrome staining and microplate method, respectively. In addition, the expression levels of fibrosis markers including collagen I, collagen III, α-SMA and TGF-β1 were inspected using quantitative real-time PCR (qRT-PCR), as well as SMAD2. Subsequently, the relative mRNA and protein level of SENP1 was also determined via qRT-PCR and western blot analysis. Next, the HSC-T6 cells of SENP1 knock-down were constructed and used to test the relative protein expression levels of α-SMA and SMAD2 in these cells. The results of hematoxylin-eosin staining, Masson's trichrome staining and microplate method turned out that the rat liver fibrosis models were constructed successfully, which was further confirmed by the increased expression of collagen I, collagen III, α-SMA and TGF-β1 in mRNA and protein level, as well as SMAD2. Then the expression of SENP1 was overexpressed in the rat liver fibrosis models induced by CCl₄ and the TGF-β1 treatment could increase the protein expression level of collagen I, collagen III and α-SMA. Lastly, the SENP1 knockdown HSC-T6 cells were successfully constructed, while the silence of SENP1 down-regulated the protein expression of α-SMA and SMAD2. In conclusion, this study provided a new regulation mechanism about the liver fibrosis process.