New aspects of hepatic fibrosis

Inhibitory effects of umbelliferone on carbon tetrachloride-induced hepatic fibrosis in rats through the TGF‑β1‑Smad signaling pathway

Hepatic fibrosis (HF) is a critical marker of advanced‑stage chronic liver disease and involves pivotal contributions from hepatic stellate cells (HSCs). Currently, there are no effective treatments for HF. Umbelliferone (7‑hydroxycoumarin; UMB) is a natural compound with significant anti‑inflammatory, antioxidant and anti‑tumor activities. However, its potential efficacy in treating HF has not been studied. The present study explored the protective effects of UMB against HF, targeting the TGF‑β1‑Smad signaling pathway to explore the underlying mechanisms of UMB. Carbon tetrachloride (CCl4) was injected intraperitoneally to induce HF in rats and primary HSCs were treated in vitro with UMB to investigate the improvement effect of UMB on HF. The levels of fibrosis markers, inflammation, oxidative stress and TGF‑β1‑Smad signaling pathway in the rat liver tissue and HSCs were detected using hematoxylin and eosin staining, enzyme‑linked immunosorbent assay, reverse transcription‑quantitative PCR, Cell Counting Kit‑8 and western blotting. The improvement in liver histopathology, liver function indexes and fibrosis markers demonstrated that UMB markedly inhibited the CCl4‑induced HF and inflammation in the rats. Additionally, UMB prominently reduced the pro‑inflammatory factors and oxidative stress levels. In vitro, UMB markedly inhibited primary HSC activation and decreased alpha‑smooth muscle actin and collagen I expression. The mechanism experiment proved that UMB inhibited the TGF‑β1‑Smad signaling pathway and ameliorated HF. The present study was the first to demonstrate, to the best of the authors' knowledge, that UMB might be a promising natural active compound for treating HF. Its therapeutic effect is associated with its modulation of the TGF‑β1‑Smad signaling pathway.

BMP1 Promotes Keloid by Inducing Fibroblast Inflammation and Fibrogenesis

Keloid is a typical fibrotic and inflammatory skin disease with unclear mechanisms and few therapeutic targets. In this study, we found that BMP1 was significantly increased in a collagen high-expressing subtype of fibroblast by reanalyzing a public single-cell RNA-sequence data set of keloid. The number of BMP1-positive fibroblast cells was increased in keloid fibrotic loci. Increased levels of BMP1 were further validated in the skin tissues and fibroblasts from keloid patients. Additionally, a positive correlation between BMP1 and the Keloid Area and Severity Index was found in keloid patients. In vitro analysis revealed collagen production, the phosphorylation levels of p65, and the IL-1β secretion decreased in BMP1 interfered keloid fibroblasts. Besides, the knockdown of BMP1 inhibited the growth and migration of keloid fibroblast cells. Mechanistically, BMP1 inhibition downregulated the noncanonical TGF-β pathways, including p-p38 and p-ERK1/2 signaling. Furthermore, we found the delivery of BMP1 siRNAs could significantly alleviate keloid in human keloid-bearing nude mice. Collectively, our results indicated that BMP1 exhibited various pathogenic effects on keloids as promoting cell proliferation, migration, inflammation, and ECM deposition of fibroblast cells by regulating the noncanonical TGF-β/p38 MAPK, and TGF-β/ERK pathways. BMP1-lowing strategies may appear as a potential new therapeutic target for keloid.

A detailed overview of quercetin: implications for cell death and liver fibrosis mechanisms

Background

Quercetin, a widespread polyphenolic flavonoid, is known for its extensive health benefits and is commonly found in the plant kingdom. The natural occurrence and extraction methods of quercetin are crucial due to its bioactive potential.

Purpose

This review aims to comprehensively cover the natural sources of quercetin, its extraction methods, bioavailability, pharmacokinetics, and its role in various cell death pathways and liver fibrosis.

Methods

A comprehensive literature search was performed across several electronic databases, including PubMed, Embase, CNKI, Wanfang database, and ClinicalTrials.gov, up to 10 February 2024. The search terms employed were "quercetin", "natural sources of quercetin", "quercetin extraction methods", "bioavailability of quercetin", "pharmacokinetics of quercetin", "cell death pathways", "apoptosis", "autophagy", "pyroptosis", "necroptosis", "ferroptosis", "cuproptosis", "liver fibrosis", and "hepatic stellate cells". These keywords were interconnected using AND/OR as necessary. The search focused on studies that detailed the bioavailability and pharmacokinetics of quercetin, its role in different cell death pathways, and its effects on liver fibrosis.

Results

This review details quercetin's involvement in various cell death pathways, including apoptosis, autophagy, pyroptosis, necroptosis, ferroptosis, and cuproptosis, with particular attention to its regulatory influence on apoptosis and autophagy. It dissects the mechanisms through which quercetin affects these pathways across different cell types and dosages. Moreover, the paper delves into quercetin's effects on liver fibrosis, its interactions with hepatic stellate cells, and its modulation of pertinent signaling cascades. Additionally, it articulates from a physical organic chemistry standpoint the uniqueness of quercetin's structure and its potential for specific actions in the liver.

Conclusion

The paper provides a detailed analysis of quercetin, suggesting its significant role in modulating cell death mechanisms and mitigating liver fibrosis, underscoring its therapeutic potential.

Multiple Roles of LOXL2 in the Progression of Hepatocellular Carcinoma and Its Potential for Therapeutic Targeting

LOXL2, a copper-dependent amine oxidase, has emerged as a promising therapeutic target in hepatocellular carcinoma (HCC). Increased LOXL2 expression in HCC has been linked with an aggressive phenotype and represents a poor prognostic factor. Here, we focus on the mechanisms through which LOXL2 orchestrates multiple oncogenic functions in HCC development. We performed a review of the current knowledge on the roles LOXL2 performs in the modulation of the HCC tumor microenvironment, formation of premetastatic niches, and epithelial-mesenchymal transition. We also highlighted the complex interplay between LOXL2 and hypoxia, angiogenesis, and vasculogenic mimicry in HCC. At the end of the review, we summarize the current LOXL2 inhibitors and discuss their potential in HCC precision treatment.

Discovery and development of benzene sulfonamide derivatives as anti-hepatic fibrosis agents

A novel benzene sulfonamide compound named IMB16-4 exhibits excellent anti-hepatic fibrosis activity in a recent study. To develop potential anti-hepatic fibrosis agents, a series of benzene sulfonamide derivatives were designed and synthesized based on the scaffold of the lead compound IMB16-4. As it turned out, most of the derivatives displayed potential anti-hepatic fibrosis activity, among which, compounds 11a, 11b, 11d, 13a, 36b, and 47b exhibited inhibition rates of 42.3%, 48.7%, 42.4%, 40.0%, 39.4%, and 49.3%, respectively, which were equivalent to the control IMB16-4 with an inhibition rate of 35.9%, Costunolide with an inhibition rate of 45.4%, and much more potent than that of Epigallocatechin gallate (EGCG) with an inhibition rate of 25.3%. Especially, compounds 46a, 46b, and 46c exhibited excellent anti-hepatic fibrosis activity with inhibition rates of 61.7%, 54.8%, and 60.7%, which were almost 1.5-fold inhibition rates of IMB16-4. In addition, compounds 46a, 46b, and 46c exhibited remarkable inhibitory activity in the gene expression of COL1A1, MMP-2, and the protein expression of COL1A1, FN, α-SMA, and TIMP-1 by inhibiting the JAK1-STAT1/3 pathway. These findings furnished valuable inspiration for the further development of anti-hepatic fibrosis agents.

Aronia melanocarpa polysaccharide ameliorates liver fibrosis through TGF-β1-mediated the activation of PI3K/AKT pathway and modulating gut microbiota

The purpose of this experiment was to investigate the anti-hepatic fibrosis effect of Aronia melanocarpa polysaccharide (AMP) on TAA-induced liver fibrosis mice and its mechanism, as well as the changes in intestinal flora in vivo. This was established with a dose of 200 mg/kg TAA (i.p) once every three days, lasting for eight weeks. Colchicine with 0.4 mg/kg, and AMP (200 and 400 mg/kg) were given by intragastric administration (i.g) after 28 days of intraperitoneal injection of TAA. AMP treatment significantly inhibited the activities of liver injury markers ALT and AST in serum. Histopathological staining demonstrated that AMP significantly reversed TAA-induced hepatocyte necrosis and collagen deposition. In addition, AMP treatment block TGF- β1/Smads pathway inhibited the production of ECM and alleviates liver fibrosis. Furthermore, AMP treatment enhanced the phosphorylation of PI3K/AKT and decreased the expression of its downstream apoptosis-related proteins in liver, thus effectively alleviating TAA-induced liver fibrosis. In addition, 16S rDNA gene sequencing analysis showed that AMP treatment helped restore the imbalanced ecosystem of gut microbes, increased the proportion of Bacteroidetes and Proteobacteria, and increased species richness. Above findings clearly show that AMP is an effective method for treating liver fibrosis, possibly by improving the gut microbiota.

Liver fibrosis quantification

Liver fibrosis (LF) is the wound healing response to chronic liver injury. LF is the endpoint of chronic liver disease (CLD) regardless of etiology and the single most important determinant of long-term liver-related clinical outcomes. Quantification of LF is important for staging, to evaluate response to treatment and to predict outcomes. LF is traditionally staged by liver biopsy. However, liver biopsy is invasive and suffers from sampling errors when biopsy size is inadequate; therefore, non-invasive tests (NITs) have found important roles in clinical care. NITs include simple laboratory-based serum tests, panels of serum tests, and imaging biomarkers. NITs are validated against the liver biopsy and will be used in the future for evaluation of nearly all CLDs with invasive liver biopsy reserved for some cases. Both serum tests and some imaging biomarkers such as elastography are currently used clinically as surrogate markers for LF. Several other imaging biomarkers are still considered research and awaiting clinical application in the future. As the evaluation of imaging biomarkers will likely become the norm in the future, understanding pathogenesis of LF is important. Knowledge of properties measured by imaging biomarkers and its correlation with LF is important to understand the application of NITs by abdominal radiologists. In this review, we present a brief overview of pathogenesis of LF, spatiotemporal evolution of LF in different CLD, and severity assessment with liver biopsy. This will be followed by a brief discussion on properties measured by imaging biomarkers and their relationship to the LF.

Human Liver Stem Cell Transplantation Alleviates Liver Fibrosis in a Rat Model of CCl4-Induced Liver Fibrosis

Background and Objectives

Mesenchymal stem cells (MSCs) elicit therapeutic effects against liver fibrosis in animal models. Human liver stem cells (HLSCs) are cells isolated from human liver tissue that have mesenchymal morphology and express MSC markers. HLSCs also possess intrahepatic stem cell properties. We introduce a rat model of liver fibrosis and trans-portal transplantation of HLSC to demonstrate alleviation of liver fibrosis.

Methods and Results

Liver fibrosis was induced by intraperitoneal injection of Carbon tetrachloride (CCl₄). Sprague Dawley rats underwent simultaneous partial hepatectomy of the left hepatic lobe and HLSC transplantation via the portal vein. Gross appearance of the liver observed following CCl₄ injection showed cholestasis and surface nodularity. Sirius red staining revealed deposition of collagen fibers in the extracellular matrix (ECM). Following HLSC transplantation, human albumin secreting cells were detected by immunohistochemistry in liver specimens. Quantitative measurements of fibrosis area stained by Sirius red were compared between baseline and post-HLSC transplant (1×10⁷ cells) following 10 weeks of CCl₄ treatment liver specimens. Fibrosis area (p<0.05), serum markers of liver inflammation and fibrosis (AST, ALT levels and APRI, p<0.05) significantly decreased from baseline after HLSC transplantation. RNA expression in liver tissues revealed significant decrease in tissue inhibitor of matrix metalloproteinase 1 (TIMP1), TIMP2 expression and increase in hepatocyte growth factor expression following HLSC transplantation (p<0.05).

Conclusions

HLSC transplantation effectively reduced the area of liver fibrosis with increased expression of factors promoting ECM degradation. These findings suggest the potential therapeutic role of HLSCs in various liver diseases presenting with liver fibrosis.

RCAN1.4 attenuates renal fibrosis through inhibiting calcineurin-mediated nuclear translocation of NFAT2

Chronic kidney disease (CKD) is thus deemed to a global health problem. Renal fibrosis, characterized by accumulation of extracellular matrix (ECM) components in the kidney, is considered a common pathway leading to CKD. Regulator of calcineurin1 (RCAN1), identified as a competitive endogenous inhibitor of the phosphatase calcineurin, participates in ECM deposition in various organs. However, the role of RCAN1 in renal fibrosis remains unclear. Here, unilateral ureteral obstruction (UUO), a well-known model to induce renal fibrosis in vivo, was performed on mice for a week. To overexpress RCAN1.4 in vivo, recombinant adeno-associated virus 9-packed RCAN1.4 over-expression plasm was employed in mice kidney. Lentivirus-packed RCAN1.4 over-expression plasm was employed to transfer into HK-2 and NRK-49F cells in vitro. The results indicated that RCAN1.4 expression was impaired both in UUO-induced renal fibrosis in vivo and TGF-β1-induced renal fibrosis in vitro. However, knocking in of RCAN1.4 suppressed the production of extracellular matrix (ECM) both in vivo and in vitro. Furthermore, in vitro, the apoptosis-related proteins, including the ratio of Bax/Bcl-2 and cleaved-caspase3, were elevated in cells transfected with RCAN1.4 overexpression plasmid. In addition, we found that RCAN1.4 could rugulated NFAT2 nuclear distribution by inhibiting calcineurin pathway. So overexpression of RCAN1.4 could reverse renal fibrosis, attenuate ECM related protein accumulation, promote apoptosis of myofibroblast via inhibiting Calcineurin/NFAT2 signaling pathway. Taken together, our study demonstrated that targeting RCAN1.4 may be therapeutic efficacy in renal fibrosis.

Role of the CXCR3‑mediated TLRs/MyD88 signaling pathway in promoting the development of hepatitis B into cirrhosis and liver cancer

Chronic hepatitis B can lead to liver cirrhosis and primary hepatocellular carcinoma. The present study aimed to investigate whether C‑X‑C motif chemokine receptor 3 (CXCR3) regulates the genes in Toll‑like receptors (TLRs)/myeloid differentiation primary response protein 88 (MyD88) signaling pathway in the development of hepatitis B into cirrhosis and liver cancer in vitro. A hepatitis B virus (HBV) overexpression lentivirus was constructed and infected into a LX‑2 cell line to obtain stable HBV‑overexpressing cells (named HBV‑LX‑2 cells). The CXCR3 gene was knocked down using small interfering RNA in HBV‑LX‑2 cells. Cell Counting Kit‑8 assays, cell scratch tests and flow cytometry were used to detect cell proliferation, migration and apoptosis, respectively. The levels of IL‑1β and IL‑6 in serum samples of patients with liver cancer were measured via ELISA, and the collagen content in liver cancer tissues was detected using Masson staining. Western blotting was used to detect the expression levels of proteins in the TLRs/MyD88 signaling pathway. Excessive fibrosis was identified in the liver cancer tissues, and the serum levels of IL‑6 and IL‑1β were abnormally increased in patients with liver cancer. It was found that interfering with CXCR3 inhibited cell proliferation and migration, as well as promoted the apoptosis of HBV‑LX‑2 cells. Moreover, interfering with CXCR3 inhibited the expression levels of collagen type I α 1 chain and the proteins in the TLRs/MyD88 pathway. In conclusion, CXCR3 knockdown could inhibit the expression levels of proteins in the TLR4/MyD88 signaling pathway, decrease cell proliferation and migration, and promote cell apoptosis, thus inhibiting the development of liver cirrhosis to liver cancer.

Hepatic stellate cells - from past till present: morphology, human markers, human cell lines, behavior in normal and liver pathology

Hepatic stellate cell (HSC), initially analyzed by von Kupffer, in 1876, revealed to be an extraordinary mesenchymal cell, essential for both hepatocellular function and lesions, being the hallmark of hepatic fibrogenesis and carcinogenesis. Apart from their implications in hepatic injury, HSCs play a vital role in liver development and regeneration, xenobiotic response, intermediate metabolism, and regulation of immune response. In this review, we discuss the current state of knowledge regarding HSCs morphology, human HSCs markers and human HSC cell lines. We also summarize the latest findings concerning their roles in normal and liver pathology, focusing on their impact in fibrogenesis, chronic viral hepatitis and liver tumors.

Molecular and cellular mechanisms of liver fibrosis and its regression

Chronic liver injury leads to liver inflammation and fibrosis, through which activated myofibroblasts in the liver secrete extracellular matrix proteins that generate the fibrous scar. The primary source of these myofibroblasts are the resident hepatic stellate cells. Clinical and experimental liver fibrosis regresses when the causative agent is removed, which is associated with the elimination of these activated myofibroblasts and resorption of the fibrous scar. Understanding the mechanisms of liver fibrosis regression could identify new therapeutic targets to treat liver fibrosis. This Review summarizes studies of the molecular mechanisms underlying the reversibility of liver fibrosis, including apoptosis and the inactivation of hepatic stellate cells, the crosstalk between the liver and the systems that orchestrate the recruitment of bone marrow-derived macrophages (and other inflammatory cells) driving fibrosis resolution, and the interactions between various cell types that lead to the intracellular signalling that induces fibrosis or its regression. We also discuss strategies to target hepatic myofibroblasts (for example, via apoptosis or inactivation) and the myeloid cells that degrade the matrix (for example, via their recruitment to fibrotic liver) to facilitate fibrosis resolution and liver regeneration.

Exploring the Multifaceted Therapeutic Potential of Withaferin A and Its Derivatives

Withaferin A (WA), a manifold studied, C28-steroidal lactone withanolide found in Withania somnifera. Given its unique beneficial effects, it has gathered attention in the era of modern science. Cancer, being considered a "hopeless case and the leading cause of death worldwide, and the available conventional therapies have many lacunae in the form of side effects. The poly pharmaceutical natural compound, WA treatment, displayed attenuation of various cancer hallmarks by altering oxidative stress, promoting apoptosis, and autophagy, inhibiting cell proliferation, reducing angiogenesis, and metastasis progression. The cellular proteins associated with antitumor pathways were also discussed. WA structural modifications attack multiple signal transduction pathways and enhance the therapeutic outcomes in various diseases. Moreover, it has shown validated pharmacological effects against multiple neurodegenerative diseases by inhibiting acetylcholesterinases and butyrylcholinesterases enzyme activity, antidiabetic activity by upregulating adiponectin and preventing the phosphorylation of peroxisome proliferator-activated receptors (PPARγ), cardioprotective activity by AMP-activated protein kinase (AMPK) activation and suppressing mitochondrial apoptosis. The current review is an extensive survey of various WA associated disease targets, its pharmacokinetics, synergistic combination, modifications, and biological activities.

Activation of TWIST Transcription by Chromatin Remodeling Protein BRG1 Contributes to Liver Fibrosis in Mice

Liver fibrosis is a complex pathophysiological process to which many different cell types contribute. Endothelial cells play versatile roles in the regulation of liver fibrosis. The underlying epigenetic mechanism is not fully appreciated. In the present study, we investigated the role of BRG1, a chromatin remodeling protein, in the modulation of endothelial cells in response to pro-fibrogenic stimuli in vitro and liver fibrosis in mice. We report that depletion of BRG1 by siRNA abrogated TGF-β or hypoxia induced down-regulation of endothelial marker genes and up-regulation of mesenchymal marker genes in cultured endothelial cells. Importantly, endothelial-specific BRG1 deletion attenuated CCl₄ induced liver fibrosis in mice. BRG1 knockdown in vitro or BRG1 knockout in vivo was accompanied by the down-regulation of TWIST, a key regulator of endothelial phenotype. Mechanistically, BRG1 interacted with and was recruited to the TWIST promoter by HIF-1α to activate TWIST transcription. BRG1 silencing rendered a more repressive chromatin structure surrounding the TWIST promoter likely contributing to TWIST down-regulation. Inhibition of HIF-1α activity dampened liver fibrosis in mice. Similarly, pharmaceutical inhibition of TWIST alleviated liver fibrosis in mice. In conclusion, our data suggest that epigenetic activation of TWIST by BRG1 contributes to the modulation of endothelial phenotype and liver fibrosis. Therefore, targeting the HIF1α-BRG1-TWIST axis may yield novel therapeutic solutions to treat liver fibrosis.

Expression of neuropeptide Y is increased in an activated human HSC cell line

Neuropeptide Y (NPY) is an abundant neuropeptide in the mammalian central and peripheral nervous systems. Transgenic mice overexpressing NPY in noradrenergic neurons have increased level of hepatic triglycerides, fatty acids and cholesterol, which contributed to the development of hepatosteatosis. However, the roles of NPY in the activation of hepatic stellate cells (HSCs) and the underlying mechanisms remain unclear. This study aimed to investigate the expression and secretion of NPY in human immortalized HSC LX-2 cells and the regulatory function of NPY on the fibrogenic response in LX-2 cells, to explore the potential association between NPY and LX-2 activation. The results showed an increase in the expression and secretion of NPY(1–36) in activated LX-2 cells. Both endogenous and exogenous NPY(1–36) induced the phosphorylation of mTOR, p70S6K, and 4EBP1 and promoted the fibrogenic response via NPY Y1 receptor subtype (NPY1R), as these responses were blocked by either an NPY1R antagonist (BIBP3226) or NPY1R knockdown. Moreover, NPY(1–36) serum levels were increased in patients with liver cirrhosis (LC) and hepatocellular carcinoma (HCC) and presented a positive relationship with MELD scores in LC patients. These findings suggest that immortalized HSCs LX-2 have the potential to produce NPY(1–36). High serum levels of NPY(1–36) is correlated with hepatic dysfunction in cirrhotic patients.

Methylation of RCAN1.4 mediated by DNMT1 and DNMT3b enhances hepatic stellate cell activation and liver fibrogenesis through Calcineurin/NFAT3 signaling

Background: Liver fibrosis is characterized by extensive deposition of extracellular matrix (ECM) components in the liver. RCAN1 (regulator of calcineurin 1), an endogenous inhibitor of calcineurin (CaN), is required for ECM synthesis during hypertrophy of various organs. However, the functional role of RCAN1 in liver fibrogenesis has not yet been addressed. Methods: We induced experimental liver fibrosis in mice by intraperitoneal injection of 10 % CCl4 twice a week. To investigate the functional role of RCAN1.4 in the progression of liver fibrosis, we specifically over-expressed RCAN1.4 in mice liver using rAAV8-packaged RCAN1.4 over-expression plasmid. Following the establishment of the fibrotic mouse model, primary hepatic stellate cells were isolated. Subsequently, we evaluated the effect of RCAN1.4 on hepatic fibrogenesis, hepatic stellate cell activation, and cell survival. The biological role and signaling events for RCAN1 were analyzed by protein-protein interaction (PPI) network. Bisulfite sequencing PCR (BSP) was used to predict the methylated CpG islands in the RCAN1.4 gene promoter. We used the chromatin immunoprecipitation (ChIP assay) to investigate DNA methyltransferases which induced decreased expression of RCAN1.4 in liver fibrosis. Results: Two isoforms of RCAN1 protein were expressed in CCl4-induced liver fibrosis mouse model and HSC-T6 cells cultured with transforming growth factor-beta 1 (TGF-β1). RCAN1 isoform 4 (RCAN1.4) was selectively down-regulated in vivo and in vitro. The BSP analysis indicated the presence of two methylated sites in RCAN1.4 promoter and the downregulated RCAN1.4 expression levels could be restored by 5-aza-2'-deoxycytidine (5-azadC) and DNMTs-RNAi transfection in vitro. ChIP assay was used to demonstrate that the decreased RCAN1.4 expression was associated with DNMT1 and DNMT3b. Furthermore, we established a CCl4-induced liver fibrosis mouse model by injecting the recombinant adeno-associated virus-packaged RCAN1.4 (rAAV8-RCAN1.4) over-expression plasmid through the tail vein. Liver- specific-over-expression of RAN1.4 led to liver function recovery and alleviated ECM deposition. The key protein (a member of the NFAT family of proteins) identified on PPI network data was analyzed in vivo and in vitro. Our results demonstrated that RCAN1.4 over-expression alleviates, whereas its knockdown exacerbates, TGF-β1-induced liver fibrosis in vitro in a CaN/NFAT3 signaling-dependent manner. Conclusions: RCAN1.4 could alleviate liver fibrosis through inhibition of CaN/NFAT3 signaling, and the anti-fibrosis function of RCAN1.4 could be blocked by DNA methylation mediated by DNMT1 and DNMT3b. Thus, RCAN1.4 may serve as a potential therapeutic target in the treatment of liver fibrosis.

ARHGEF4-mediates the actin cytoskeleton reorganization of hepatic stellate cells in 3-dimensional collagen matrices

The actin cytoskeleton of hepatic stellate cells (HSCs) is reorganized when they are cultured in 3D collagen matrices. Here, we investigated the molecular mechanism of actin cytoskeleton reorganization in HSCs cultured in 3D floating collagen matrices (FCM) compared to those on 2D polystyrene surfaces (PS). First, we found that the generation of dendritic cellular processes was controlled by Rac1. Next, we examined the differential gene expression of HSCs cultured on 2D PS and in 3D FCM by RNA-Seq and focused on the changes of actin cytoskeleton reorganization-related molecular components and guanine nucleotide exchange factors (GEFs). The results showed that the expression of genes associated with actin cytoskeleton reorganization-related cellular components, filopodia and lamellipodia, were significantly decreased, but podosome-related genes was significantly increased in 3D FCM. Furthermore, we found that a Rac1-specific GEF, ARHGEF4, played roles in morphological changes, migration and podosome-related gene expression in HSCs cultured in 3D FCM.

Abbreviations: 2D PS: 2-dimensional polystyrene surface; 3D FCM: 3-dimensional floating collagen matrices; ARHGEF4: Rho guanine nucleotide exchange factor 4; ARHGEF6: Rho guanine nucleotide exchange factor 6; GEF: guanine nucleotide exchange factor; HSC: hepatic stellate cell

Nonalcoholic Fatty Liver Disease Demonstrates a Pre-fibrotic and Premalignant Molecular Signature

BACKGROUND

Metabolic syndrome contributing to nonalcoholic fatty liver disease (NAFLD) can lead to hepatic dysfunction, steatohepatitis, cirrhosis, and hepatocellular carcinoma.

AIMS

In this study, we tested whether diet-induced fatty liver in a mouse model physiologically mimicked human NAFLD, and whether transcriptional alterations in mouse fatty liver signified risk for the development of hepatitis, cirrhosis, and/or hepatocellular carcinoma.

METHODS

SAMP6 strain mice were fed a low-fat diet or high-fat diet (HFD) for 6 months. Mouse livers were isolated and subjected to histology, immunohistochemistry, and whole transcriptome RNA sequencing. Sequences were aligned to the mouse reference genome, and gene expression signatures were analyzed using bioinformatics tools including Cufflinks, Pathview, Cytoscape, ClueGO, and GOstats.

RESULTS

Consistent with NAFLD, livers from HFD-fed mice demonstrated steatosis, high levels of inflammation, an up-regulation of genes encoding proteins associated with the complement pathway and immune responses, and down-regulation of those associated with metabolic processes. These livers also showed an up-regulation of genes associated with fibrosis and malignant transformation but no histological evidence of either pathobiology or DNA damage.

CONCLUSIONS

HFD-fed mice exhibited NAFLD that had incompletely transitioned from fatty liver to NASH. Importantly, bioinformatics approaches identified pre-fibrotic and premalignant signatures, suggesting that the pathogenesis of both fibrosis and cancer may initiate in fatty livers well before associated histological changes are evident.

High-mobility group box 1 induces endoplasmic reticulum stress and activates hepatic stellate cells

Liver fibrosis is a worldwide clinical issue. The activation of hepatic stellate cells (HSCs) is the central event during the hepatic fibrotic response. However, the exact mechanisms related to HSC activation and the connection between hepatocytes and HSCs remain unclear. We elucidated the mechanism by which the nuclear-damage-associated molecular pattern molecule, high-mobility group box 1 (HMGB1) was released from the impaired hepatocytes and induced endoplasmic reticulum stress to activate HSCs. In this work, we demonstrated that HMGB1 can be released from hepatocytes and the released HMGB1 activates the HSCs via ER stress at the transcriptional level which was dependent on the activation of both the TLR4 and RAGE signaling pathways rather than the TLR2 signaling pathway. HMGB1 induction of proinflammatory cytokines interleukin (IL)-1β and IL-18 release was dependent on ER stress. In vivo, stable inhibition of HMGB1 suppressed liver fibrosis. These results suggest that under damage condition, HMGB1 can be secreted from injured hepatocytes and activates TLR4- and RAGE signaling pathways to induce ER stress which activates HSCs. Moreover, HMGB1 can produce multiple inflammatory mediators through ER stress, which, in turn, promote liver fibrosis.

Clinico-Pathological Importance of TGF-β/Phospho-Smad Signaling during Human Hepatic Fibrocarcinogenesis

Chronic viral hepatitis is a global public health problem, with approximately 570 million persons chronically infected. Hepatitis B and C viruses increase the risk of morbidity and mortality from liver cirrhosis, hepatocellular carcinoma (HCC), and extrahepatic complications that develop. Hepatitis virus infection induces transforming growth factor (TGF)-β, which influences microenvironments within the infected liver. TGF-β promotes liver fibrosis by up-regulating extracellular matrix production by hepatic stellate cells. TGF-β is also up-regulated in patients with HCC, in whom it contributes importantly to bringing about a favorable microenvironment for tumor growth. Thus, TGF-β is thought to be a major factor regulating liver fibrosis and carcinogenesis. Since TGF-β carries out regulatory signaling by influencing the phosphorylation of Smads, we have generated several kinds of phospho-specific antibodies to Smad2/3. Using these, we have identified three types of phospohorylated forms: COOH-terminally phosphorylated Smad2/3 (pSmad2C and pSmad3C), linker phosphorylated Smad2/3 (pSmad2L and pSmad3L), and dually phosphorylated Smad3 (pSmad2L/C and pSmad3L/C). TGF-β-mediated pSmad2/3C signaling terminates cell proliferation; on the other hand, cytokine-induced pSmad3L signaling accelerates cell proliferation and promotes fibrogenesis. This review addresses TGF-β/Smad signal transduction in chronic liver injuries and carcinogenic processes. We also discuss the reversibility of Smad signaling after antiviral therapy.

A humanized mouse model of liver fibrosis following expansion of transplanted hepatic stellate cells

Hepatic stellate cells (HSCs) are major contributors to liver fibrosis, as hepatic injuries may cause their transdifferentiation into myofibroblast-like cells capable of producing excessive extracellular matrix proteins. Also, HSCs can modulate engraftment of transplanted hepatocytes and contribute to liver regeneration. Therefore, understanding the biology of human HSCs (hHSCs) is important, but effective methods have not been available to address their fate in vivo. To investigate whether HSCs could engraft and repopulate the liver, we transplanted GFP-transduced immortalized hHSCs into immunodeficient NOD/SCID mice. Biodistribution analysis with radiolabeled hHSCs showed that after intrasplenic injection, the majority of transplanted cells rapidly translocated to the liver. GFP-immunohistochemistry demonstrated that transplanted hHSCs engrafted alongside hepatic sinusoids. Prior permeabilization of the sinusoidal endothelial layer with monocrotaline enhanced engraftment of hHSCs. Transplanted hHSCs remained engrafted without relevant proliferation in the healthy liver. However, after CCl₄ or bile duct ligation-induced liver damage, transplanted hHSCs expanded and contributed to extracellular matrix production, formation of bridging cell-septae and cirrhosis-like hepatic pseudolobules. CCl₄-induced injury recruited hHSCs mainly to zone 3, whereas after bile duct ligation, hHSCs were mainly in zone 1 of the liver lobule. Transplanted hHSCs neither transdifferentiated into other cell types nor formed tumors in these settings. In conclusion, a humanized mouse model was generated by transplanting hHSCs, which proliferated during hepatic injury and inflammation, and contributed to liver fibrosis. The ability to repopulate the liver with transplanted hHSCs will be particularly significant for mechanistic studies of cell-cell interactions and fibrogenesis within the liver.

Arkadia protein expression is reduced in the liver during the progression of hepatic fibrosis

Arkadia is able to degrade key signaling molecules in the transforming growth factor (TGF)‑β1 signaling pathway; however, the expression of Arkadia in the liver during development and progression of TGF‑β1/Smad signaling‑regulated hepatic fibrosis remains to be elucidated. The present study aimed to examine Arkadia expression in the livers of two rat models of hepatic fibrosis induced by bile duct ligation and carbon tetrachloride intoxication, and in human liver samples from patients with hepatic fibrosis. Expression was analyzed by quantitative polymerase chain reaction, immunohistochemistry and western blot analysis. The results indicated that Arkadia was predominantly expressed in the cytoplasm of cholangiocytes and hepatocytes. The protein expression levels of Arkadia were significantly decreased in fibrotic livers, whereas the mRNA expression levels of Arkadia were significantly increased in fibrotic livers compared with in nonfibrotic livers. In conclusion, these data indicated that Arkadia may regulate the pathogenesis and progression of hepatic fibrosis.

The fibrotic tumor stroma

Intratumoral fibrosis results from the deposition of a cross-linked collagen matrix by cancer-associated fibroblasts (CAFs). This type of fibrosis has been shown to exert mechanical forces and create a biochemical milieu that, together, shape intratumoral immunity and influence tumor cell metastatic behavior. In this Review, we present recent evidence that CAFs and tumor cells are regulated by provisional matrix molecules, that metastasis results from a change in the type of stromal collagen cross-link, and that fibrosis and inflammation perpetuate each other through proteolytic and chemotactic mediators released into the tumor stroma. We also discuss aspects of the emerging biology that have potential therapeutic value.

Therapeutic activity of plant-derived alkaloid conophylline on metabolic syndrome and neurodegenerative disease models

Increasing metabolic syndromes including type-2 diabetes mellitus, obesity, and steatohepatitis are serious problems in most countries in the world. Neurodegenerative diseases such as Alzheimer, Parkinson's, and Huntington's diseases are increasing in many countries. However, therapy for these diseases is not sufficient yet. Thus, effective chemotherapy for these diseases is being expected. Conophylline is an alkaloid isolated from the leaves of Ervatamia microphylla and related plants. It was found to induce beta-cell differentiation in the precursor pancreatic cells. Oral administration of this compound ameliorated type-2 diabetes mellitus model in mice and rats. Later, fibrosis of the pancreatic islets was found to be greatly reduced by conophylline in the pancreatic islets. It also inhibited chemically induced liver cirrhosis. Further study indicated that conophylline inhibited non-alcoholic steatohepatitis in the model mice. On the one hand, loss of autophagy often causes protein aggregation to give neural cell death. Conophylline was found to activate autophagy in cultured neural cells. Activation of autophagy ameliorated cellular models of Parkinson's and Huntington's diseases. Thus, conophylline is likely to be useful for the development of chemotherapy for metabolic and neurodegenerative diseases.

Knockdown of histidine-rich calcium-binding protein (HRC) suppresses liver fibrosis by inhibiting the activation of hepatic stellate cells

The histidine-rich calcium-binding protein (HRC) is a regulator of Ca²⁺ homeostasis and it plays a significant role in hepatocellular carcinoma (HCC) progression. However, the relationship between HRC and liver fibrogenesis is still unknown. Our data demonstrates that HRC was upregulated in fibrotic liver and activated hepatic stellate cells (HSCs). TGF-β treatment increased α-SMA and HRC expression dose-dependently in HSCs. Repression of HRC reduced α-SMA, CTGF and collagen expression, and inhibited HSC proliferation and migration. In addition, we found that the anti-fibrosis effect of HRC knockdown was associated with endoplasmic reticulum (ER) stress. Silencing of HRC decreased the expression of ER stress and autophagy markers. Moreover, ER stress agonist thapsigargin (TG) enhanced, whereas ER stress antagonist 4-phenylbutyric acid (4-PBA) alleviated HSCs activation and autophagy. In conclusion, these data indicate that depletion of HRC inhibited HSC activation through the ER stress pathway, and HRC may be a potential regulator of liver fibrosis.

Dihydroartemisinin alleviates bile duct ligation-induced liver fibrosis and hepatic stellate cell activation by interfering with the PDGF-βR/ERK signaling pathway

Liver fibrosis represents a frequent event following chronic insult to trigger wound healing responses in the liver. Activation of hepatic stellate cells (HSCs), which is a pivotal event during liver fibrogenesis, is accompanied by enhanced expressions of a series of marker proteins and pro-fibrogenic signaling molecules. Artemisinin, a powerful antimalarial medicine, is extracted from the Chinese herb Artemisia annua L., and can inhibit the proliferation of cancer cells. Dihydroartemisinin (DHA), the major active metabolite of artemisinin, is able to attenuate lung injury and fibrosis. However, the effect of DHA on liver fibrosis remains unclear. The aim of this study was to investigate the effect of DHA on bile duct ligation-induced injury and fibrosis in rats. DHA improved the liver histological architecture and attenuated collagen deposition in the fibrotic rat liver. Experiments in vitro showed that DHA inhibited the proliferation of HSCs and arrested the cell cycle at the S checkpoint by altering several cell-cycle regulatory proteins. Moreover, DHA reduced the protein expressions of a-SMA, α1 (I) collagen and fibronectin, being associated with interference of the platelet-derived growth factor β receptor (PDGF-βR)-mediated ERK pathway. These data collectively revealed that DHA relieved liver fibrosis possibly by targeting HSCs via the PDGF-βR/ERK pathway. DHA may be a therapeutic antifibrotic agent for the treatment of hepatic fibrosis.

Attenuation of liver fibrosis by herbal compound 861 via upregulation of BMP-7/Smad signaling in the bile duct ligation model rat

Herbal compound 861 (Cpd 861) exerts an anti-fibrotic effect in patients with hepatic fibrosis; however, the anti-fibrotic mechanism has yet to be fully elucidated. The present study aimed to explore the mechanistic basis for the anti-fibrotic effect, with a focus on bone morphogenetic protein 7 (BMP-7)/Smad signaling in a bile duct ligation (BDL)-induced liver fibrosis rat model. Following the induction of hepatic fibrosis, rats induced by BDL were treated with 9 g/kg Cpd 861 daily or an equal volume of saline for 28 days. Serum samples were prepared for monitoring the levels of alanine transaminase, aspartate transaminase and total bilirubin, and direct bilirubin analyses and liver samples were used to investigate gene expression, protein localization and protein expression analysis using real‑time quantitative polymerase chain reaction, immunohistochemistry and western blotting. The results revealed the attenuation of liver fibrosis by Cpd 861 in the histological and biochemical experiments. BMP‑7 and phospho (p)‑Smad1/5/8 were localized predominantly in the cytoplasm of hepatocytes. In comparison with the saline‑treated BDL rats, Cpd 861 markedly upregulated the gene expression of BMP‑7 and Smad5, as well as the protein expression of BMP‑7 and Smad1/5. In addition, p-Smad1/5/8 protein expression was markedly increased by Cpd 861 in the BDL model. These results indicated that Cpd 861 alleviates hepatic fibrosis possibly via the upregulation and activation of BMP-7/Smad signaling in hepatic fibrotic rats.

Early type I collagen deposition is associated with prognosis in biliary atresia

BACKGROUND

Biliary atresia (BA) is a cholestatic liver disease of children that progresses to hepatic fibrosis. BA is the main indication of pediatric liver transplantation (LTx). Histopathological markers in liver biopsies could be useful for predicting progression to end-stage disease.

OBJECTIVE

To establish histopathological or immunohistochemical markers in liver biopsies of BA patients and correlate those markers with prognosis.

METHOD

Histological analysis of biliary alterations and morphometric assessment of liver fibrosis were performed, in addition to indirect immunofluorescence assays (IF) for type I, III, IV and V collagens in initial and final liver biopsies of 36 patients with BA who underwent Kasai hepatoportoenterostomy (KPE) and LTx in the last 20years at a single center.

RESULTS

Histopathological markers had no correlation with evolutive time until LTx. The perisinusoidal deposition of type III and V collagens was more prominent in the initial biopsies (p<0.01), whereas deposition of type I and IV collagens indicated progression (p<0.01). Patients with large amounts of perisinusoidal type I collagen in the initial biopsies had worse progression time curves until LTx (p=0.04).

CONCLUSION

Morphometric assessment of perisinusoidal deposition of type I collagen by IF in the initial biopsy can correlate with progression time to LTx in post-surgical BA.

Reversible Human TGF-β Signal Shifting between Tumor Suppression and Fibro-Carcinogenesis: Implications of Smad Phospho-Isoforms for Hepatic Epithelial-Mesenchymal Transitions

Epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) are observed during both physiological liver wound healing and the pathological fibrotic/carcinogenic (fibro-carcinogenetic) process. TGF-β and pro-inflammatory cytokine are considered to be the major factors accelerating liver fibrosis and promoting liver carcinogenesis. Smads, consisting of intermediate linker regions connecting Mad homology domains, act as the intracellular mediators of the TGF-β signal transduction pathway. As the TGF-β receptors, c-Jun N-terminal kinase and cyclin-dependent kinase, differentially phosphorylate Smad2/3, we have generated numerous antibodies against linker (L) and C-terminal (C) phosphorylation sites in Smad2/3 and identified four types of phosphorylated forms: cytostatic COOH-terminally-phosphorylated Smad3 (pSmad3C), mitogenic pSmad3L (Ser-213) signaling, fibrogenic pSmad2L (Ser-245/250/255)/C signaling and migratory pSmad2/3L (Thr-220/179)/C signaling. After acute liver injury, TGF-β upregulates pSmad3C signaling and terminates pSmad3L (Ser-213)-mediated hepatocyte proliferation. TGF-β and pro-inflammatory cytokines cooperatively enhance collagen synthesis by upregulating pSmad2L (Thr-220)/C and pSmad3L (Thr-179)/C pathways in activated hepatic stellate cells. During chronic liver injuries, hepatocytes persistently affected by TGF-β and pro-inflammatory cytokines eventually become pre-neoplastic hepatocytes. Both myofibroblasts and pre-neoplastic hepatocyte exhibit the same carcinogenic (mitogenic) pSmad3L (Ser-213) and fibrogenic pSmad2L (Ser-245/250/255)/C signaling, with acquisition of fibro-carcinogenic properties and increasing risk of hepatocellular carcinoma (HCC). Firstly, we review phospho-Smad-isoform signalings in epithelial and mesenchymal cells in physiological and pathological conditions and then consider Smad linker phosphorylation as a potential target for pathological EMT during human fibro-carcinogenesis, because human Smad phospho-isoform signals can reverse from fibro-carcinogenesis to tumor-suppression in a process of MET after therapy.

NLRC5 regulates TGF-β1-induced proliferation and activation of hepatic stellate cells during hepatic fibrosis

Therapeutic management of liver fibrosis remains an unsolved clinical problem. Hepatic accumulation of extracellular matrix, mainly collagen, is mediated by the production of transforming growth factor-β1 (TGF-β1) in hepatic stellate cells (HSCs). NLRC5, the largest member of the NLR protein family, has recently been identified as a critical regulator of immune responses. Novel evidence shows that NLRC5 is an important negative modulator of inflammatory pathways. Herein, we determined the regulation of NLRC5 in liver fibrogenesis and its underlying mechanisms. We have shown that NLRC5 was upregulated in human liver fibrotic tissues. Overexpression of NLRC5 resulted in an upregulation of collagen 1 and α-smooth muscle actin expression in HSC LX-2 cells, which was inhibited by NLRC5 knockdown with its siRNA. Furthermore, NLRC5 deficiency significantly suppressed TGF-β1-induced proliferation but increased apoptosis (i.e., increased caspases-3, DR4 and DR5) in LX-2 cells. In addition, knockdown of NLRC5 promoted the activation of NF-κB signaling pathways but abrogated phosphorylation of Smad2 and Smad3 proteins in response to TGF-β1. These results indicate that NLRC5 is a potent pro-fibrogenic molecule for HSC activation through TGF-β1/Smad and NF-κB signaling pathways. NLRC5 inhibition would be a promising therapeutic avenue for treating hepatic fibrosis.

Effects of the dihydrolipoyl histidinate zinc complex against carbon tetrachloride-induced hepatic fibrosis in rats

PURPOSE

This study investigated the effects of an antioxidant, dihydrolipoyl histidinate zinc complex (DHLHZn), on the hepatic fibrosis in the carbon tetrachloride (CCl4) rat model.

METHODS

The animals were divided into three groups: control, CCl4, and CCl4+DHLHZn. A histological assessment of the liver fibrosis was performed using stained liver samples. The oxidative stress and antioxidant levels were evaluated by measuring the malondialdehyde (MDA) and glutathione (GSH) levels in the liver. In addition, cultured human hepatic stellate cells (LI90) were exposed to antimycin-A (AMA) and divided into four groups: control, DHLHZn, AMA, and AMA+DHLHZn. The effects of DHLHZn on AMA-induced fibrosis were evaluated by measuring the expression of transforming growth factor (TGF)-β1 and collagen α1 (I).

RESULTS

The hepatic fibrosis in the CCl4+DHLHZn group was attenuated compared to that in the CCl4 group. The MDA levels in the CCl4+DHLHZn group were significantly lower than those of the CCl4 group, whereas the GSH levels in the CCl4+DHLHZn group were significantly higher than those of the CCl4 group. Furthermore, the relative mRNA expression of TGF-β1 and collagen α1 (I) in the AMA+DHLHZn group was significantly lower than that in the AMA group.

CONCLUSION

DHLHZn may attenuate the hepatic fibrosis induced by CCl4 by decreasing the degree of oxidative stress.

MicroRNAs as Important Players in Host-hepatitis B Virus Interactions

Hepatitis B virus (HBV) infection, a major public health problem, causes acute and chronic hepatitis that is often complicated by liver cirrhosis and hepatocellular carcinoma. The pathogenic mechanisms of HBV-related liver disease are not well understood, and the current licensed therapies are not effective in permanently clearing virus from the circulation. In recent years, the role of micro-ribonucleic acids (miRNAs) in HBV infection has attracted great interest. Cellular miRNAs can influence HBV replication directly by binding to HBV transcripts and indirectly by targeting cellular factors relevant to the HBV life cycle. They are also involved in the regulation of cellular genes and signaling pathways that have critical roles in HBV pathogenesis. HBV infection, in turn, can trigger changes in cellular miRNA expression that are associated with distinctive miRNA expression profiles depending on the phase of liver disease. These alterations in miRNA expression have been linked to disease progression and hepatocarcinogenesis. We provide here an up to date review regarding the field of miRNAs and HBV interplay and highlight the potential utility of miRNAs as diagnostic biomarkers and therapeutic targets for the management of HBV-related liver disease.

Effects of small interfering RNA-mediated downregulation of the Krüppel-like factor 4 gene on collagen metabolism in human hepatic stellate cells

The nuclear transcription factor Krüppel-like factor 4 (KLF4) has an important role in cellular biological processes. However, the influence of KLF4 on collagen metabolism remains to be elucidated. In the present study, the effects and underlying mechanism of action of KLF4 on collagen metabolism was investigated in human hepatic stellate cells (HSC), by downregulating KLF4 expression using small interfering RNA (siRNA). The effects of KLF4 silencing by three predesigned siRNAs (siRNA1‑3) were evaluated using both reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) and western blotting in the human LX2 HSC line. The mRNA expression levels of KLF4 were decreased by ~34, 40, and 69% in the siRNA1, siRNA2, and siRNA3 groups, respectively, as compared with the control group. These results were concordant with the protein expression levels of KLF4, as determined by western blot analysis. In the siRNA3 group, the quantity of type Ⅰ and type III collagen, and the expression levels of collagen metabolism proteins including matrix metalloproteinase‑1 (MMP‑1) and tissue inhibitors of metalloproteinases‑1 (TIMP‑1), were determined using both RT‑qPCR and western blotting. Both the mRNA and protein expression levels of type I and type III collagen were significantly decreased in the siRNA3 group, as compared with the control group. The mRNA and protein expression levels of TIMP‑1 were also significantly reduced in the siRNA3‑treated cells, whereas the mRNA and protein expression levels of MMP‑1 were significantly upregulated. Furthermore, KLF4 gene silencing significantly decreased the expression levels of numerous cytokines, including transforming grow factor‑β1, tumor necrosis factor‑α, and interleukin‑1β. The results of the present study provide evidence of siRNA‑mediated silencing of KLF4 expression, which may promote extracellular matrix (ECM) degradation, and inhibition of ECM synthesis. Therefore, KLF4 may be a promising target for the development of novel antifibrotic therapies.

Suppressive effect of SATB1 on hepatic stellate cell activation and liver fibrosis in rats

Liver fibrosis is a worldwide clinical issue. Activation of hepatic stellate cells (HSCs) is the central event during liver fibrosis. We investigated the role of SATB1 in HSC activation and liver fibrogenesis. The results show that SATB1 expression is reduced during HSC activation. Additionally, SATB1 inhibits HSC activation, proliferation, migration, and collagen synthesis. Furthermore, CTGF, a pro-fibrotic agent, is also significantly inhibited by SATB1 through the Ras/Raf-1/MEK/ERK/Ets-1 pathway. In vivo, SATB1 deactivates HSCs and attenuates fibrosis in TAA-induced fibrotic rat livers. These data indicate that SATB1 plays an important role in HSC activation and liver fibrosis.

Fibronectin peptides as potential regulators of hepatic fibrosis through apoptosis of hepatic stellate cells

The turnover of extracellular matrix (ECM) components can generate signals that regulate several cellular functions such as proliferation, differentiation, and apoptosis. During liver injury, matrix metalloproteases (MMPs) production is enhanced and increased levels of peptides derived from extracellular matrix proteins can be generated. Synthetic peptides with sequences present in extracellular matrix proteins were previously found to induce both stimulating and apoptotic effects on several cell types including the inflammatory cells monocytes/macrophages. Therefore, in inflammatory liver diseases, locally accumulated peptides could be also important in regulating hepatic fibrosis by inducing apoptosis of hepatic stellate cells (HSC), the primary cellular source of extracellular matrix components. Here, we describe the apoptotic effect of fibronectin peptides on the cell line of human hepatic stellate cells LX-2 based on oligonucleosomal DNA fragmentation, caspase-3 and -9 activation, Bcl-2 depletion, and accumulation of Bax protein. We also found that these peptides trigger the activation of Src kinase, which in turn mediated the increase of JNK and p38 activities. By the use of specific inhibitors we demonstrated the involvement of Src, JNK, and p38 in apoptosis induced by fibronectin peptides on HSC. Moreover, fibronectin peptides increased iNOS expression in human HSC, and specific inhibition of iNOS significantly reduced the sustained activity of JNK and the programmed cell death caused by these peptides. Finally, the possible regulatory effect of fibronectin peptides in liver fibrosis was further supported by the ability of these peptides to induce metalloprotease-9 (MMP-9) expression in human monocytes.

Conophylline suppresses hepatic stellate cells and attenuates thioacetamide-induced liver fibrosis in rats

BACKGROUND & AIMS

Conophylline (CnP) is a vinca alkaloid purified from a tropical plant and inhibits activation of pancreatic stellate cells. We investigated the effect of CnP on hepatic stellate cells (HSC) in vitro. We also examined whether CnP attenuates hepatic fibrosis in vivo.

METHOD

We examined the effect of CnP on the expression of α-smooth muscle actin (α-SMA) and collagen-1, DNA synthesis and apoptosis in rat HSC and Lx-2 cells. We also examined the effect of CnP on hepatic fibrosis induced by thioacetamide (TAA).

RESULTS

In rat HSC and Lx-2 cells, CnP reduced the expression of α-SMA and collagen-1. CnP inhibited DNA synthesis induced by serum. CnP also promoted activation of caspase-3 and induced apoptosis as assessed by DNA ladder formation and TUNEL assay. In contrast, CnP did not induce apoptosis in AML12 cells. We then examined the effect of CnP on TAA-induced cirrhosis. In TAA-treated rats, the surface of the liver was irregular and multiple nodules were observed. Histologically, formation of pseudolobules surrounded by massive fibrous tissues was observed. When CnP was administered together with TAA, the surface of the liver was smooth and liver fibrosis was markedly inhibited. Collagen content was significantly reduced in CnP-treated liver.

CONCLUSION

Conophylline suppresses HSC and induces apoptosis in vitro. CnP also attenuates formation of the liver fibrosis induced by TAA in vivo.

Inhibitory effect of nuclear factor-κB decoy oligodeoxynucleotide on liver fibrosis through regulation of the epithelial-mesenchymal transition

The epithelial-mesenchymal transition (EMT) has been recognized to occur during embryonic development, fibrosis, and tumor metastasis. Nuclear factor (NF)-κB plays a central role in mediating the inflammation and wound-healing responses during liver fibrogenesis. However, the involvement of NF-κB during EMT in liver cells remains unidentified. To develop a therapeutic approach to EMT during liver fibrosis, we examined the inhibition of transcription factor NF-κB, using a decoy oligodeoxynucleotide (ODN) strategy in liver fibrosis in vitro and in vivo. NF-κB decoy ODN contains consensus binding sequences of the NF-κB-binding site. NF-κB decoy ODN effectively suppresses transforming growth factor-β(1)-induced EMT in AML12 murine hepatocytes. Liver fibrosis induced by CCl(4) administration was suppressed by NF-κB decoy ODN. Furthermore, NF-κB decoy ODN was shown to inhibit the EMT process in fibrotic liver in vivo. This study demonstrates the feasibility of NF-κB decoy ODN treatment for preventing liver fibrosis via EMT processes.

TGF-β/Smad signaling during hepatic fibro-carcinogenesis (review)

After hepatitis virus infection, plasma transforming growth factor (TGF)-β increases in either the acute or chronic inflammatory microenvironment. Although TGF-β is upregulated in patients with hepatocellular carcinoma, it is one of the most potent growth inhibitors for hepatocytes. This cytokine also upregulates extracellular matrix (ECM) production of hepatic stellate cells. Therefore, TGF-β is considered to be the major factor regulating liver carcinogenesis and accelerating liver fibrosis. Smad2 and Smad3 act as the intracellular mediators of TGF-β signal transduction pathway. We have generated numerous antibodies against individual phosphorylation sites in Smad2/3, and identified 3 types of phosphorylated forms (phospho-isoforms): COOH-terminally phosphorylated Smad2/3 (pSmad2C and pSmad3C), linker phosphorylated Smad2/3 (pSmad2L and pSmad3L) and dually phosphorylated Smad2/3 (pSmad2L/C and pSmad3L/C). These Smad phospho-isoforms are categorized into 3 groups: cytostatic pSmad3C signaling, mitogenic pSmad3L signaling and invasive/fibrogenic pSmad2L/C signaling. In this review, we describe differential regulation of TGF-β/Smad signaling after acute or chronic liver injuries. In addition, we consider how chronic inflammation associated with hepatitis virus infection promotes hepatic fibrosis and carcinogenesis (fibro-carcinogenesis), focusing on alteration of Smad phospho-isoform signaling. Finally, we show reversibility of Smad phospho-isoform signaling after therapy against hepatitis virus infection.

Cellular mechanisms of tissue fibrosis. 6. Purinergic signaling and response in fibroblasts and tissue fibrosis

Tissue fibrosis occurs as a result of the dysregulation of extracellular matrix (ECM) synthesis. Tissue fibroblasts, resident cells responsible for the synthesis and turnover of ECM, are regulated via numerous hormonal and mechanical signals. The release of intracellular nucleotides and their resultant autocrine/paracrine signaling have been shown to play key roles in the homeostatic maintenance of tissue remodeling and in fibrotic response post-injury. Extracellular nucleotides signal through P2 nucleotide and P1 adenosine receptors to activate signaling networks that regulate the proliferation and activity of fibroblasts, which, in turn, influence tissue structure and pathologic remodeling. An important component in the signaling and functional responses of fibroblasts to extracellular ATP and adenosine is the expression and activity of ectonucleotideases that attenuate nucleotide-mediated signaling, and thereby integrate P2 receptor- and subsequent adenosine receptor-initiated responses. Results of studies of the mechanisms of cellular nucleotide release and the effects of this autocrine/paracrine signaling axis on fibroblast-to-myofibroblast conversion and the fibrotic phenotype have advanced understanding of tissue remodeling and fibrosis. This review summarizes recent findings related to purinergic signaling in the regulation of fibroblasts and the development of tissue fibrosis in the heart, lungs, liver, and kidney.

Saikosaponin A of Bupleurum chinense (Chaihu) elevates bone morphogenetic protein 4 (BMP-4) during hepatic stellate cell activation

BACKGROUND

Saikosaponin a (SSa) is a compound extracted from a Chinese herb which has been widely used in treating liver diseases such as liver fibrosis. However, the mechanism of SSa in treatment of liver fibrosis still remain unclear. Our previous study demonstrated that BMP4 stimulated the expression of smooth muscle alpha actin (α-SMA) in the liver. Therefore, the current study investigates the effect of SSa on BMP4 expression during hepatic stellate cell activation in a human hepatic stellate cell line.

METHODS

LX-2 cells were cultured in DMEM/F12 with fetal bovine serum and treated with SSa in different times and concentrations. The expression of BMP4 was examined by both RT-PCR and western blot analysis. WST-1 proliferation reagent was used to evaluate cell proliferation. α-SMA and Bax protein expression was determined by western blot analysis.

RESULTS

Both mRNA and protein levels of BMP-4 were significantly inhibited in LX-2 cells after 5 μM SSa treatment. SSa significantly inhibited LX-2 proliferation at the concentration of 5μM while BMP-4 had no effect on LX-2 proliferation. BMP-4 increased α-SMA expression in LX-2 while SSa reduced α-SMA expression. In addition SSa could neutralize the effect of BMP-4 on α-SMA expression. SSd also inhibited BMP4 expression but not NG. Bax protein expression was induced in these cells by 5 μM SSa.

CONCLUSION

SSa could down-regulate BMP-4 expression and inhibit hepatic stellate cell activation. Therefore, SSa could be used for treatment of liver disease with elevated BMP-4 expression.

Aryl hydrocarbon receptor-dependent induction of liver fibrosis by dioxin

The contribution of environmental pollutants to liver fibrosis is an important and poorly explored issue. In vitro studies suggest that the environmental pollutant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and other aryl hydrocarbon receptor (AhR) ligands induce several genes that are known to be upregulated during liver fibrosis. Our aim was to determine whether exposure to such pollutants can lead to liver fibrosis and to characterize the mechanisms of action. Mice were treated for 2, 14, or 42 days, once a week with 25 µg/kg of TCDD. Gene and protein expression, in vitro and in vivo, as well as liver histology were investigated for each treatment. Treatment of mice with TCDD for 2 weeks modified the hepatic expression of markers of fibrosis such as collagen 1A1 and α-smooth muscle actin. This is not observed in AhR knockout mice. Following 6 weeks of treatment, histological features of murine hepatic fibrosis became apparent. In parallel, the levels of inflammatory cytokines (interleukin-1 beta, tumor necrosis factor α) and of markers of activated fibroblasts(fibroblast-specific protein 1) were found to be upregulated. Interestingly, we also found increased expression of genes of the TGF-β pathway and a concomitant decrease of miR-200a levels. Because the transcription factors of the Snail family were shown to be involved in liver fibrosis, we studied their regulation by TCDD. Two members of the Snail family were increased, whereas their negative targets, the epithelial marker E-cadherin and Claudin 1, were decreased. Further, the expression of mesenchymal markers was increased. Finally, we confirmed that Snai2 is a direct transcriptional target of TCDD in the human hepatocarcinoma cell line, HepG2. The AhR ligand, TCDD, induces hepatic fibrosis by directly regulating profibrotic pathways.

Semaphorin 7A contributes to TGF-β-mediated liver fibrogenesis

Semaphorin7A (SEMA7A) is a membrane-anchored protein involved in immune and inflammatory responses, exerting an effect on pulmonary fibrosis. Thus, we aimed to investigate the role of SEMA7A in hepatic fibrosis. Liver injury was induced in vivo by carbon tetrachloride i.p. injection or bile duct ligation in wild-type and SEMA7A knockout (KO) mice. Human and mouse liver samples and primary mouse hepatic cell populations were used for Western blot analysis, quantitative real-time RT-PCR, and immunohistochemistry. SEMA7A is highly expressed in hepatic stellate cells (HSCs). The expression of SEMA7A and its receptor β1-integrin subunit increase during liver injury and in activated HSCs. Transforming growth factor β-stimulated HSCs showed increased expression of SEMA7A in a SMAD2/3-independent manner, leading to increased expression of fibrogenic and inflammation markers. This pattern was significantly blunted in SEMA7A KO HSCs. Overexpression of SEMA7A in HSCs showed increased fibrogenic and inflammation markers expression. In vivo, SEMA7A KO mice treated with carbon tetrachloride and bile duct ligation developed reduced fibrosis versus wild-type mice. Moreover, SEMA7A expression increased in liver samples of patients with fibrosis versus healthy controls. SEMA7A was expressed in the liver and was increased in the course of liver fibrosis, both in mice and in humans. SEMA7A was mainly expressed in HSCs with respect to other cell types in the liver and plays a critical role in regulating fibrosis.

Physiological and biochemical basis of clinical liver function tests: a review

OBJECTIVE

To review the literature on the most clinically relevant and novel liver function tests used for the assessment of hepatic function before liver surgery.

BACKGROUND

Postoperative liver failure is the major cause of mortality and morbidity after partial liver resection and develops as a result of insufficient remnant liver function. Therefore, accurate preoperative assessment of the future remnant liver function is mandatory in the selection of candidates for safe partial liver resection.

METHODS

A MEDLINE search was performed using the key words "liver function tests," "functional studies in the liver," "compromised liver," "physiological basis," and "mechanistic background," with and without Boolean operators.

RESULTS

Passive liver function tests, including biochemical parameters and clinical grading systems, are not accurate enough in predicting outcome after liver surgery. Dynamic quantitative liver function tests, such as the indocyanine green test and galactose elimination capacity, are more accurate as they measure the elimination process of a substance that is cleared and/or metabolized almost exclusively by the liver. However, these tests only measure global liver function. Nuclear imaging techniques ((99m)Tc-galactosyl serum albumin scintigraphy and (99m)Tc-mebrofenin hepatobiliary scintigraphy) can measure both total and future remnant liver function and potentially identify patients at risk for postresectional liver failure.

CONCLUSIONS

Because of the complexity of liver function, one single test does not represent overall liver function. In addition to computed tomography volumetry, quantitative liver function tests should be used to determine whether a safe resection can be performed. Presently, (99m)Tc-mebrofenin hepatobiliary scintigraphy seems to be the most valuable quantitative liver function test, as it can measure multiple aspects of liver function in, specifically, the future remnant liver.

High mobility group box-1 promotes the proliferation and migration of hepatic stellate cells via TLR4-dependent signal pathways of PI3K/Akt and JNK

BACKGROUND

The migration of hepatic stellate cells (HSCs) is essential to the hepatic fibrotic response, and recently High-mobility group box 1 (HMGB1) has been shown up-regulated during liver fibrosis. Nevertheless, whether HMGB1 can modulate the proliferation and migration of HSCs is poorly understood, as well as the involved intracellular signaling. In this study, we examined the effect of HMGB1 on proliferation, migration, pro-fibrotic function of HSCs and investigated whether toll-like family of receptor 4 (TLR4) dependent signal pathway is involved in the intracellular signaling regulation.

METHODOLOGY/PRINCIPAL FINDINGS

Modified transwell chamber system to mimic the space of Disse was used to evaluate the migration of human primary HSCs, and the protein expressions of related signal factors were evaluated by western blot. Cell proliferation was analyzed by MTT assay, the pro-fibrotic functions of HSCs by qRT-PCR and ELISA respectively. Recombinant human HMGB1 could significantly promote migration of HSCs under both haptotactic and chemotactic stimulation, especially the latter. Human TLR4 neutralizing antibody could markedly inhibit HMGB1-induced migration of HSCs. HMGB1 could enhance the phosphorylation of JNK and PI3K/Akt, and TLR4 neutralizing antibody inhibited HMGB1-enhanced phosphorylation of JNK and PI3K/Akt and activation of NF-κB. JNK inhibitor (SP600125) and PI3K inhibitor (LY 294002) significantly inhibited HMGB1-induced proliferation and migration of HSCs, and also reduced HMGB1-enhanced related collagen expressions and pro-fibrotic cytokines production.

CONCLUSIONS/SIGNIFICANCE

HMGB1 could significantly enhance migration of HSCs in vitro, and TLR4-dependent JNK and PI3K/Akt signal pathways are involved in the HMGB1-induced proliferation, migration and pro-fibrotic effects of HSCs, which indicates HMGB1 might be an effective target to treat liver fibrosis.

Hepatic stellate cells increase in Toxoplasma gondii infection in mice

BACKGROUND

Toxoplasma gondii is a ubiquitous protozoan parasite that can infect humans and animals. The severity of toxoplasmosis varies according to the immune status of the individual, parasite strain, and host species. In mammalian species, it has been observed that severe lesions of acute toxoplasmosis form in visceral organs such as the liver, lung, and spleen. Some epidemiological studies have reported an association of T. gondii infection with liver cirrhosis.

METHODS

Acute infection was induced in fifteen 30-day-old normal Swiss albino mice. The mice were infected by intraperitoneal inoculation of 5000 T. gondii RH strain tachyzoites. The mice were sacrificed in groups of 5 at 2, 4, and 6 days after inoculation. Another group of 5 mice were used as the controls. Anti-glial fibrillary acidic protein (GFAP) and anti-T. gondii antibodies were used to compare GFAP-immunoreactive cells and anti-T. gondii-immunopositive areas in the liver between the T. gondii-infected groups and the healthy controls, respectively.

RESULTS

There was a significant correlation between the numbers of GFAP-positive hepatic stellate cells (HSCs) when they were compared with T. gondii antigen immunostaining (p < 0.05). The amount of T. gondii immunostaining increased significantly with the increase in the number of HSCs.

CONCLUSIONS

There is a significant relationship between the number of HSCs and T. gondii antigens, which may represent an active role of HSCs in liver pathology and the pathobiology of T. gondii-related hepatitis.

Hepatic stellate cells and portal fibroblasts are the major cellular sources of collagens and lysyl oxidases in normal liver and early after injury

Liver fibrosis is characterized by excessive deposition of extracellular matrix proteins by myofibroblasts derived from hepatic stellate cells and portal fibroblasts. Activation of these precursors to myofibroblasts requires matrix stiffness, which results in part from increased collagen cross-linking mediated by lysyl oxidase (LOX) family proteins. The aims of this study were to characterize the mechanical changes of early fibrosis, to identify the cells responsible for LOX production in early injury, and to determine which cells in normal liver produce collagens and elastins, which serve as substrates for LOXs early after injury. Hepatocytes and liver nonparenchymal cells were isolated from normal and early-injured liver and examined immediately for expression of LOXs and matrix proteins. We found that stellate cells and portal fibroblasts were the major cellular sources of fibrillar collagens and LOXs in normal liver and early after injury (1 day after bile duct ligation and 2 and 7 days after CCl(4) injury). Activity assays using stellate cells and portal fibroblasts in culture demonstrated significant increases in LOX family enzymatic activity as cells became myofibroblastic. LOX family-mediated deoxypyridinoline and pyridinoline cross-links increased after CCl(4)-mediated injury. There was a significant association between liver stiffness (as quantified by the shear storage modulus G') and deoxypyridinoline levels; increased deoxypyridinoline levels were also coincident with significantly increased elastic resistance to large strain deformations, consistent with increased cross-linking of the extracellular matrix. These data suggest a model in which the liver is primed to respond quickly to injury, activating potential mechanical feed-forward mechanisms.