Fibrogenic actions of acetaldehyde are β-catenin dependent but Wingless independent: a critical role of nucleoredoxin and reactive oxygen species in human hepatic stellate cells

Role of an interdependent Wnt, GSK3-β/β-catenin and HB-EGF/EGFR mechanism in arsenic-induced hippocampal neurotoxicity in adult mice

We previously reported the neurotoxic effects of arsenic in the hippocampus. Here, we explored the involvement of Wnt pathway, which contributes to neuronal functions. Administering environmentally relevant arsenic concentrations to postnatal day-60 (PND60) mice demonstrated a dose-dependent increase in hippocampal Wnt3a and its components, Frizzled, phospho-LRP6, Dishevelled and Axin1 at PND90 and PND120. However, p-GSK3-β(Ser9) and β-catenin levels although elevated at PND90, decreased at PND120. Additionally, treatment with Wnt-inhibitor, rDkk1, reduced p-GSK3-β(Ser9) and β-catenin at PND90, but failed to affect their levels at PND120, indicating a time-dependent link with Wnt. To explore other underlying factors, we assessed epidermal growth factor receptor (EGFR) pathway, which interacts with GSK3-β and appears relevant to neuronal functions. We primarily found that arsenic reduced hippocampal phosphorylated-EGFR and its ligand, Heparin-binding EGF-like growth factor (HB-EGF), at both PND90 and PND120. Moreover, treatment with HB-EGF rescued p-GSK3-β(Ser9) and β-catenin levels at PND120, suggesting their HB-EGF/EGFR-dependent regulation at this time point. Additionally, rDkk1, LiCl (GSK3-β-activity inhibitor), or β-catenin protein treatments induced a time-dependent recovery in HB-EGF, indicating potential inter-dependent mechanism between hippocampal Wnt/β-catenin and HB-EGF/EGFR following arsenic exposure. Fluorescence immunolabeling then validated these findings in hippocampal neurons. Further exploration of hippocampal neuronal survival and apoptosis demonstrated that treatment with rDkk1, LiCl, β-catenin and HB-EGF improved Nissl staining and NeuN levels, and reduced cleaved-caspase-3 levels in arsenic-treated mice. Supportively, we detected improved Y-Maze and Passive Avoidance performances for learning-memory functions in these mice. Overall, our study provides novel insights into Wnt/β-catenin and HB-EGF/EGFR pathway interaction in arsenic-induced hippocampal neurotoxicity.

Size-dependent toxicity of polystyrene microplastics on the gastrointestinal tract: Oxidative stress related-DNA damage and potential carcinogenicity

Microplastics (MPs) and nanoplastics (NPs) have been generally regarded as emerging pollutants and received worldwide attention in recent years. Water and food consumption are the primary pathways for human exposure to MPs/NPs, thus gastrointestinal tracts may be susceptible to their toxicity. Although the recent report has indicated the presence of MPs/NPs in multiple human organs, little is known about their gastric effects. Therefore, this study focused on the adverse effects of polystyrene microplastics (PS-MPs) on gastric epithelium in vivo and in vitro. Surface-enhanced Raman spectroscopy (SERS) revealed the distribution of PS-MPs was associated with their particle sizes, and predominantly concentrated in gastric tissues. Gastric barrier injury and mitochondrial damage were observed in rats after exposure to PS-MPs. Compared with the larger ones, polystyrene nanoplastics (PS-NPs) more significantly reduced the activity of antioxidant enzymes while enhancing the level of MDA, 8-OhdG and γ-H2AX. Meanwhile, PS-MPs caused upregulation of β-catenin/YAP through redox-dependent regulation of nucleoredoxin (NXN) and dishevelled (Dvl). These findings supported the size-dependent effects of PS-MPs on oxidative stress and DNA damage. Moreover, the redox-dependent activation of the β-catenin/YAP cascade suggested a novel toxic mechanism for PS-MPs and implied the potential carcinogenic effects.

NXN suppresses metastasis of hepatocellular carcinoma by promoting degradation of Snail through binding to DUB3

The poor prognosis of hepatocellular carcinoma (HCC) could be attributed to its high metastasis rate. Here, we report the role of nucleoredoxin (NXN), a multifunctional redox-active protein, in HCC metastasis. The expression of NXN in HCC tissues was measured by immunohistochemistry. The role of NXN on HCC proliferation was determined by CCK-8, EdU and colony formation assays in vitro and subcutaneous tumor formation model in vivo. Transwell and wound healing assays and tail vein injection model were performed to assess the function of NXN on HCC metastasis. Co-immunoprecipitation assay was performed to examine the interaction among NXN, Snail and DUB3. Our results showed that NXN was downregulated in HCC tissues compared to adjacent liver tissues. Patients with low NXN expression had shorter overall survival (OS) time (P < 0.001) than those with high NXN expression. Biologically, ectopic expression of NXN significantly inhibited the proliferation and metastasis of HCC cells both in vitro and in vivo by suppressing epithelial-mesenchymal transition (EMT). Mechanistically, NXN promoted the ubiquitin-proteasome-mediated degradation of Snail through interaction with DUB3. Further, depletion of Snail abolished NXN-inhibited cell proliferation and metastasis. In summary, NXN suppressed the proliferation and metastasis of HCC by inhibiting DUB3-mediated deubiquitylation of Snail protein. Our study demonstrates that NXN, DUB3 and Snail complex functioned as an important regulatory mechanism of HCC progression and indicates a potential therapeutic approach for the treatment of HCC metastasis.

Is Nucleoredoxin a Master Regulator of Cellular Redox Homeostasis? Its Implication in Different Pathologies

Nucleoredoxin (NXN), an oxidoreductase enzyme, contributes to cellular redox homeostasis by regulating different signaling pathways in a redox-dependent manner. By interacting with seven proteins so far, namely disheveled (DVL), protein phosphatase 2A (PP2A), phosphofructokinase-1 (PFK1), translocation protein SEC63 homolog (SEC63), myeloid differentiation primary response gene-88 (MYD88), flightless-I (FLII), and calcium/calmodulin-dependent protein kinase II type alpha (CAMK2A), NXN is involved in the regulation of several key cellular processes, including proliferation, organogenesis, cell cycle progression, glycolysis, innate immunity and inflammation, motility, contraction, protein transport into the endoplasmic reticulum, neuronal plasticity, among others; as a result, NXN has been implicated in different pathologies, such as cancer, alcoholic and polycystic liver disease, liver fibrogenesis, obesity, Robinow syndrome, diabetes mellitus, Alzheimer’s disease, and retinitis pigmentosa. Together, this evidence places NXN as a strong candidate to be a master redox regulator of cell physiology and as the hub of different redox-sensitive signaling pathways and associated pathologies. This review summarizes and discusses the current insights on NXN-dependent redox regulation and its implication in different pathologies.

Current Perspectives on the Immunosuppressive Niche and Role of Fibrosis in Hepatocellular Carcinoma and the Development of Antitumor Immunity

Immune checkpoint inhibitors have become the mainstay of treatment for hepatocellular carcinoma (HCC). However, they are ineffective in some cases. Previous studies have reported that genetic alterations in oncogenic pathways such as Wnt/β-catenin are the important triggers in HCC for primary refractoriness. T-cell exhaustion has been reported in various tumors and is likely to play a prominent role in the emergence of HCC due to chronic inflammation and cirrhosis-associated immune dysfunction. Immunosuppressive cells including regulatory T-cells and tumor-associated macrophages infiltrating the tumor are associated with hyperprogressive disease in the early stages of immune checkpoint inhibitor treatment. In addition, stellate cells and tumor-associated fibroblasts create an abundant desmoplastic environment by producing extracellular matrix. This strongly contributes to epithelial to mesenchymal transition via signaling activities including transforming growth factor beta, Wnt/β-catenin, and Hippo pathway. The abundant desmoplastic environment has been demonstrated in pancreatic ductal adenocarcinoma and cholangiocarcinoma to suppress cytotoxic T-cell infiltration, PD-L1 expression, and neoantigen expression, resulting in a highly immunosuppressive niche. It is possible that a similar immunosuppressive environment is created in HCC with advanced fibrosis in the background liver. Although sufficient understanding is required for the establishment of immune therapies of HCC, further investigations are still required in this field.

Pathophysiological Aspects of Alcohol Metabolism in the Liver

Alcoholic liver disease (ALD) is a globally prevalent chronic liver disease caused by chronic or binge consumption of alcohol. The liver is the major organ that metabolizes alcohol; therefore, it is particularly sensitive to alcohol intake. Metabolites and byproducts generated during alcohol metabolism cause liver damage, leading to ALD via several mechanisms, such as impairing lipid metabolism, intensifying inflammatory reactions, and inducing fibrosis. Despite the severity of ALD, the development of novel treatments has been hampered by the lack of animal models that fully mimic human ALD. To overcome the current limitations of ALD studies and therapy development, it is necessary to understand the molecular mechanisms underlying alcohol-induced liver injury. Hence, to provide insights into the progression of ALD, this review examines previous studies conducted on alcohol metabolism in the liver. There is a particular focus on the occurrence of ALD caused by hepatotoxicity originating from alcohol metabolism.

Flightless-I is a potential biomarker for the early detection of alcoholic liver disease

Alcoholic liver disease (ALD) is closely linked to oxidative stress induction. Antioxidant enzymes balance oxidative stress and function as intermediary signaling regulators. Nucleoredoxin (NXN), an antioxidant enzyme, regulates physiological processes through redox-sensitive interactions. NXN interacts with myeloid differentiation primary response gene-88 (MYD88) and flightless-I (FLII) to regulate toll-like receptor 4 (TLR4)/MYD88 pathway activation, but FLII also regulates key cell processes and is secreted into the bloodstream. However, the effects of chronic ethanol consumption recapitulated by either ethanol alone or in combination with lipopolysaccharides (LPS), as a two-hit ALD model, on FLII/NXN/MYD88 complex and FLII secretion have not been explored yet. In this study, we have demonstrated that ethanol feeding increased FLII protein levels, its nuclear translocation and plasma secretion, and modified its tissue distribution both in vivo and in vitro ALD models. Ethanol increased MYD88/FLII interaction ratio, and decreased NXN/MYD88 interaction ratio but this was partially reverted by two-hit model. While ethanol and two-hit model increased MYD88/TLR4 interaction ratio, two-hit model significantly decreased FLII nuclear translocation and its plasma secretion. Ethanol and LPS provoked similar effects in vitro; however, NXN overexpression partially reverted these alterations, and ethanol alone increased FLII secretion into culture medium. In summary, by analyzing the response of FLII/NXN/MYD88 complex during ALD early progression both in vivo and in vitro, we have discovered that the effects of chronic ethanol consumption disrupt this complex and identified FLII as a candidate non-invasive plasma biomarker for the early detection of ALD.

Glycogen synthase kinase-3β: a promising candidate in the fight against fibrosis

Fibrosis exists in almost all organs/tissues of the human body, plays an important role in the occurrence and development of diseases and is also a hallmark of the aging process. However, there is no effective prevention or therapeutic method for fibrogenesis. As a serine/threonine (Ser/Thr)-protein kinase, glycogen synthase kinase-3β (GSK-3β) is a vital signaling mediator that participates in a variety of biological events and can inhibit extracellular matrix (ECM) accumulation and the epithelial-mesenchymal transition (EMT) process, thereby exerting its protective role against the fibrosis of various organs/tissues, including the heart, lung, liver, and kidney. Moreover, we further present the upstream regulators and downstream effectors of the GSK-3β pathway during fibrosis and comprehensively summarize the roles of GSK-3β in the regulation of fibrosis and provide several potential targets for research. Collectively, the information reviewed here highlights recent advances vital for experimental research and clinical development, illuminating the possibility of GSK-3β as a novel therapeutic target for the management of tissue fibrosis in the future.

Heme Oxygenase-1 Suppresses Wnt Signaling Pathway in Nonalcoholic Steatohepatitis-Related Liver Fibrosis

Methods

Mice were fed with a methionine-choline-deficient (MCD) diet for 8 weeks to induce steatohepatitis-related liver fibrosis and were treated with HO-1 inducer Hemin and inhibitor ZnPP. Mouse sera were collected for the biochemical analysis, and livers were obtained for further histological observation and gene expression analysis. HSC-T6 cells were cultured for the in vitro study and were administrated with Hemin and si-HO-1 to induce or inhibit the expression of HO-1. qPCR and Western blot were used to assess the mRNA and protein levels of genes.

Results

MCD-fed mice developed marked macrovesicular steatosis, focal necrosis, and inflammatory infiltration and pericellular fibrosis in liver sections. Administration of Hemin could significantly ameliorate the severity of steatosis, inflammation, and fibrosis and also could decrease the serum ALT and AST. We demonstrated that HO-1 induction was able to downregulate the key regulator of the canonical Wnt pathway Wnt1 and the noncanonical Wnt pathway Wnt5a. The downstream factors of the Wnt pathway β-catenin and NFAT5 were inhibited by Hemin, but GSK-3β was upregulated compared to the MCD group, which were consistent with the in vitro study. Hemin markedly inhibited the TGF-β1/Smad signaling pathway in both in vivo and in vitro studies.

Conclusion

Our study demonstrated that HO-1 inhibited the activation of canonical and noncanonical Wnt signaling pathways in NASH-related liver fibrosis. Thus, these results may suggest a new therapeutic strategy for NASH-related liver fibrosis.

Exosomal MALAT1 derived from hepatic cells is involved in the activation of hepatic stellate cells via miRNA-26b in fibrosis induced by arsenite

In the liver microenvironment, interactions among diverse types of hepatic cells are involved in liver fibrosis. In fibrotic tissues, exosomes act as transporters in intercellular communication. Long non-coding RNAs (lncRNAs) are involved in the activation of hepatic stellate cells (HSCs), which are participants in liver fibrosis. However, the functions of exosomal lncRNAs in liver fibrosis induced by arsenite are undefined. The purposes of the present study were (a) to determine if lncRNAs secreted from human hepatic (L-02) cells exposed to arsenite are shuttled to hepatic stellate LX-2 cells and (b) to establish their effects on LX-2 cells. In mice, MALAT1 was overexpressed in the progression of liver fibrosis induced by arsenite as well as in L-02 cells exposed to arsenite. Co-cultures with arsenite-treated L-02 cells induced the activation of LX-2 cells and overexpression of MALAT1. Arsenite-treated L-02 cells transported MALAT1 into LX-2 cells. Downregulation of MALAT1, which reduced the MALAT1 levels in exosomes derived from arsenite-treated L-02 cells, inhibited the activation of LX-2 cells. Additionally, exosomal MALAT1 derived from arsenite-treated L-02 cells promoted the activation of LX-2 cells via microRNA-26b regulation of COL1A2. Furthermore, circulating exosomal MALAT1 was up-regulated in people exposed to arsenite. In sum, exosomes derived from arsenite-treated hepatic cells transferred MALAT1 to HSCs, which induced their activation. These findings support the concept that, during liver fibrosis induced by arsenite, exosomal lncRNAs are involved in cell-cell communication.

Role of phospholipase D in bleomycin-induced mitochondrial reactive oxygen species generation, mitochondrial DNA damage, and pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a pernicious lung disease characterized by alveolar epithelial apoptosis, dysregulated repair of epithelial injury, scar formation, and respiratory failure. In this study, we identified phospholipase D (PLD)-generated phosphatidic acid (PA) signaling in the development of pulmonary fibrosis (PF). Of the PLD isoenzymes, the protein expression of PLD2, but not PLD1, was upregulated in lung tissues from IPF patients and bleomycin challenged mice. Both PLD1 (Pld1^-/-)- and PLD2 (Pld2^-/-)-deficient mice were protected against bleomycin-induced lung inflammation and fibrosis, thereby establishing the role of PLD in fibrogenesis. The role of PLD1 and PLD2 in bleomycin-induced lung epithelial injury was investigated by infecting bronchial airway epithelial cells (Beas2B) with catalytically inactive mutants of PLD (hPLD1-K898R or mPld2-K758R) or downregulation of expression of PLD1 or PLD2 with siRNA. Bleomycin stimulated mitochondrial (mt) superoxide production, mtDNA damage, and apoptosis in Beas2B cells, which was attenuated by the catalytically inactive mutants of PLD or PLD2 siRNA. These results show a role for PLD1 and PLD2 in bleomycin-induced generation of mt reactive oxygen species, mt DNA damage, and apoptosis of lung epithelial cells in mice. Thus, PLD may be a novel therapeutic target in ameliorating experimental PF in mice.

Ethanol targets nucleoredoxin/dishevelled interactions and stimulates phosphatidylinositol 4-phosphate production in vivo and in vitro

Nucleoredoxin (NXN) is a redox-regulating protein potentially targeted by reactive oxygen species (ROS). It regulates molecular pathways that participate in several key cellular processes. However, the role of NXN in the alcohol liver disease (ALD) redox regulation has not been fully understood. Here, we investigated the effects of ethanol and ethanol plus lipopolysaccharide, a two-hit liver injury model (Ethanol/LPS), on NXN/dishevelled (DVL) interaction and on DVL-dependent phosphoinositides production both in mouse liver and in a co-culture system consisting of human hepatic stellate cells (HSC) and ethanol metabolizing-VL17A human hepatocyte cells. Ethanol and two-hit model increased Nxn protein and mRNA expression, and 4-hydroxynonenal adducts. Two-hit model promoted Nxn nuclear translocation and Dvl/Phosphatidylinositol 4-kinase type-IIα (Pi4k2a) interaction ratio but surprisingly decreased Dvl protein and mRNA levels and reverted ethanol-induced Nxn/Dvl and Dvl/frizzled (Fzd) interaction ratios. Ethanol resulted in a significant increase of Dvl protein and mRNA expression, and decreased Nxn/Dvl interaction ratio but promoted the interaction of Dvl with Fzd and Pi4k2a; formation of this complex induced phosphatidylinositol 4-phosphate [PI(4)P] production. Ethanol and LPS treatments provoked similar alterations on NXN/DVL interaction and its downstream effect in HSC/VL17A co-culture system. Interestingly, ROS and glutathione levels as well as most of ethanol-induced alterations were modified by NXN overexpression in the co-culture system. In conclusion, two-hit model of ethanol exposure disrupts NXN/DVL homeostatic status to allow DVL/FZD/PI4K2A complex formation and stimulates PI(4)P production. These results provide a new mechanism showing that NXN also participates in the regulation of phosphoinositides production that is altered by ethanol during alcoholic liver disease progression.

Emerging role and therapeutic implication of Wnt signaling pathways in liver fibrosis

Activation of hepatic stellate cells (HSCs) is a pivotal cellular event in liver fibrosis. Therefore, improving our understanding of the molecular pathways that are involved in these processes is essential to generate new therapies for liver fibrosis. Greater knowledge of the role of the Wnt signaling pathway in liver fibrosis could improve understanding of the liver fibrosis pathogenesis. The aim of this review is to describe the present knowledge about the Wnt signaling pathway, which significantly participates in liver fibrosis and HSC activation, and look ahead on new perspectives of Wnt signaling pathway research. Moreover, we will discuss the different interactions with Wnt signaling pathway-regulated liver fibrosis. The Wnt signaling pathway modulates several important aspects of function, including cell proliferation, activation and differentiation. Targeting the Wnt signaling pathway can be a promising direction in liver fibrosis treatment. We discuss new perspectives of Wnt signaling pathway activation in liver fibrosis. For example, antagonist to Wnt and Wnt ligands could inhibit liver fibrosis by regulating Wnt/β-catenin signaling pathway. These findings identify the Wnt signaling pathway as a potentially important for therapeutic targets in liver fibrosis. Future studies are needed in order to find safer and more effective Wnt-based drugs.

Wenyang Huazhuo Tongluo formula inhibits fibrosis via suppressing Wnt/β-catenin signaling pathway in a Bleomycin-induced systemic sclerosis mouse model

Background

Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrosis of the skin and internal organs. So far, no Western medicine treatment can completely inhibit or reverse the progress of SSc, while at the same time, our previous series of studies have shown that the treatment of SSc by the Wenyang Huazhuo Tongluo formula (WYHZTL), a Chinese herbal decoction, shows a delightful prospect. The aim of this study is to further investigate the mechanism of anti-fibrosis of WYHZTL formula in SSc mouse model.

Methods

The Bleomycin-induced SSc mouse model was treated with saline (BLM), high-dosage of WYHZTL formula (WYHZTL-H), medium-dosage of WYHZTL formula (WYHZTL-M), low-dosage of WYHZTL formula (WYHZTL-L) and XAV-939, a small molecule inhibitor of Wnt/β-catenin signaling pathway, by the intragastric administration and intraperitoneal injection, respectively. The mRNA and protein levels of Wnt/β-catenin signaling pathway associated genes, fibrosis markers and histopathology were detected by reverse transcription-quantitative polymerase chain reaction, Western blotting and hematoxylin/eosin-staining. The levels of Wnt1, CTGF and DKK1 protein in serum were detected by enzyme-linked immunosorbent assay.

Results

Compared with BLM group, the WYHZTL formula and XAV-939 could significantly inhibit the thickness of the skin tissue of the SSc mouse model. The mRNA expression levels of GSK3β and DKK1 in the WYHZTL formula and XAV-939-treated group were significantly higher than those in the BLM group, while Wnt1, β-catenin, TCF4, cyclin D1, survivin, VEGF, CTGF, FN1, collagen I/III were decreased. Compared with BLM group, the protein expression levels of GSK3β and DKK1 in the WYHZTL formula and XAV-939-treated group were upregulated, while Wnt1, β-catenin, cyclin D1, survivin, CTGF, FN1, collagen I/III were downregulated. WYHZTL formula and XAV-939 could inhibit expression of Wnt1 and CTGF, but promoted DKK1 in serum. Furthermore, WYHZTL-H seemed more effective than WYHZTL-M and/or XAV-939 on regulating Wnt1, β-catenin, TCF4, GSK3β, DKK1, cyclin D1, survivin, VEGF, CTGF, FN1 and collagen I/III.

Conclusion

This present study demonstrates that WYHZTL formula has anti-fibrosis effect in Bleomycin-induced SSc mouse model in a dosage-dependent manner, and the molecular mechanism may be related to the inhibition of Wnt/β-catenin signaling pathway.

Electronic supplementary material

The online version of this article (10.1186/s13020-018-0175-z) contains supplementary material, which is available to authorized users.

Inhibition of aldehyde dehydrogenase 1 enhances the cytotoxic effect of retinaldehyde on A549 cancer cells

We hypothesized that aldehyde dehydrogenase1 (ALDH1) protects cancer cells from retinaldehyde-induced cytotoxicity, and that targeting this enzyme would enhance the therapeutic effect of retinaldehyde. ALDEFLUOR™ assays showed high ALDH activity in A549 and H522 cancer cells and low activity in H1666 and T47D cancer cells. Immunoblots showed that expression of ALDH1A1 and ALDH1A3 was high in A549 and H522 cells, but low in H1666 cells. HPLC confirmed that N, N-diethylaminobenzaldehyde (DEAB) inhibits ALDH-mediated disposal of retinaldehyde in A549 cells and lysates. Treatment of A549 cells with retinaldehyde in the presence of DEAB augmented reactive oxygen species production and decreased glucose uptake and oxygen consumption. Importantly, DEAB substantially potentiated the ability of retinaldehyde to dose-dependently suppress the survival of A549 and H522 cells, whereas the added effect of DEAB was minor in H1666 and T47D cells. Gene silencing with specific siRNA revealed that ALDH1A1 contributed to protection of A549 cells against retinaldehyde toxicity. These results demonstrate that ALDH1 confers protection against retinaldehyde toxicity in cancer cells.

Purinergic P2X7 receptor mediates acetaldehyde-induced hepatic stellate cells activation via PKC-dependent GSK3β pathway

The activation of hepatic stellate cells (HSCs) is an essential part in the development of alcoholic liver fibrosis (ALF). In this study, stimulated HSCs with 200μM acetaldehyde for 48h was used to imitate alcoholic liver fibrosis in vitro. The western blot and qRT-PCR results showed that P2X7R expression was significantly increased in the activation of HSCs after acetaldehyde treatment. Interestingly, activation of P2X7R by stimulating with P2X7R agonist BzATP significantly promoted acetaldehyde-induced CyclinD1 expression, cell proportion in S phase, inflammatory response, and the protein and mRNA levels of α-SMA, collagen I. In contrast, blockage of P2X7R by stimulating with the inhibitor A438079 or transfecting with specific siRNA dramatically suppressed acetaldehyde-induced HSCs activation. Furthermore, PKC activation treated with PMA could obviously up-regulate the expression of α-SMA and collagen I and the phosphorylation of GSK3β, while inhibition of PKC significantly reduced GSK3β activation. Moreover, GSK3β inhibition harvested a dramatic decrease of the mRNA and protein levels of α-SMA and collagen I by suppressing GSK3β phosphorylation. Taken together, these results suggested that purinergic P2X7R mediated acetaldehyde-induced activation of HSCs via PKC-dependent GSK3β pathway, which maybe a novel target for limiting HSCs activation.

Metabolic derivatives of alcohol and the molecular culprits of fibro-hepatocarcinogenesis: Allies or enemies?

Chronic intake of alcohol undoubtedly overwhelms the structural and functional capacity of the liver by initiating complex pathological events characterized by steatosis, steatohepatitis, hepatic fibrosis and cirrhosis. Subsequently, these initial pathological events are sustained and ushered into a more complex and progressive liver disease, increasing the risk of fibro-hepatocarcinogenesis. These coordinated pathological events mainly result from buildup of toxic metabolic derivatives of alcohol including but not limited to acetaldehyde (AA), malondialdehyde (MDA), CYP2E1-generated reactive oxygen species, alcohol-induced gut-derived lipopolysaccharide, AA/MDA protein and DNA adducts. The metabolic derivatives of alcohol together with other comorbidity factors, including hepatitis B and C viral infections, dysregulated iron metabolism, abuse of antibiotics, schistosomiasis, toxic drug metabolites, autoimmune disease and other non-specific factors, have been shown to underlie liver diseases. In view of the multiple etiology of liver diseases, attempts to delineate the mechanism by which each etiological factor causes liver disease has always proved cumbersome if not impossible. In the case of alcoholic liver disease (ALD), it is even more cumbersome and complicated as a result of the many toxic metabolic derivatives of alcohol with their varying liver-specific toxicities. In spite of all these hurdles, researchers and experts in hepatology have strived to expand knowledge and scientific discourse, particularly on ALD and its associated complications through the medium of scientific research, reviews and commentaries. Nonetheless, the molecular mechanisms underpinning ALD, particularly those underlying toxic effects of metabolic derivatives of alcohol on parenchymal and non-parenchymal hepatic cells leading to increased risk of alcohol-induced fibro-hepatocarcinogenesis, are still incompletely elucidated. In this review, we examined published scientific findings on how alcohol and its metabolic derivatives mount cellular attack on each hepatic cell and the underlying molecular mechanisms leading to disruption of core hepatic homeostatic functions which probably set the stage for the initiation and progression of ALD to fibro-hepatocarcinogenesis. We also brought to sharp focus, the complex and integrative role of transforming growth factor beta/small mothers against decapentaplegic/plasminogen activator inhibitor-1 and the mitogen activated protein kinase signaling nexus as well as their cross-signaling with toll-like receptor-mediated gut-dependent signaling pathways implicated in ALD and fibro-hepatocarcinogenesis. Looking into the future, it is hoped that these deliberations may stimulate new research directions on this topic and shape not only therapeutic approaches but also models for studying ALD and fibro-hepatocarcinogenesis.

Increased Pygo2 expression in liver of patients with hepatitis B virus-related fibrosis

BACKGROUND & AIMS

It has been reported that Wnt/β-catenin signalling pathway played a key role in liver fibrosis and that Pygo2 was an important mediator in β-catenin induced pathway. However, the role of Pygo2 in liver fibrogenesis was unknown. Our study was to investigate the expression of Pygo2 and its diagnostic value in patients with HBV-related liver fibrosis.

METHODS

Hundred and sixty-four patients with HBV infection underwent liver biopsy and liver stiffness measurement (LSM) by transient elastography (Fibroscan(®) ; Echosens). Liver function was tested by routine biochemical examinations. Liver condition was assessed by haematoxylin and eosin (H&E) and Masson's trichrome staining. The expression of Pygo2 in liver tissue was measured by Real-time PCR and immunohistochemistry, respectively, while the serum levels of Pygo2 were detected by ELISA. The relationship between degree of liver fibrosis and Pygo2 expression was assessed by correlation analysis. Receiver operating characteristics (ROC) analysis was used to evaluate diagnostic accuracy of serum Pygo2, LSM and their combination.

RESULTS

The mRNA and protein levels of Pygo2 in HBV-infected patients were all higher than in normal persons (P < 0.05 respectively). Moreover, Pygo2 expression increased along with the progression of liver fibrosis (P < 0.05 respectively). The trend of serum Pygo2 agreed with its expression in liver tissue. The combination of serum Pygo2 and LSM had a significantly higher area under the curve than Pygo2 or LSM alone (P < 0.05 respectively).

CONCLUSIONS

This study suggested that Pygo2 was involved in HBV-induced liver fibrogenesis. Pygo2 is a valuable biomarker for the evaluation of fibrosis in HBV-infected patients.

Effect of Yinshao powder on expression of transforming growth factor-β1 and β-catenin in hepatic fibrosis in rats

AIM: To investigate the effect of traditional Chinese medicine Yinshao powder on the expression of transforming growth factor-β1 (TGF-β1) and β-catenin in hepatic fibrosis in rats to clarify the molecular mechanism of clearing heat, expelling damp and promoting blood circulation.

METHODS: Sixty adult male Wistar rats were divided randomly into six groups: a normal control group, a model group, low-, medium- and high-dose Yinshao powder groups and a colchicine group. Hepatic fibrosis was induced by giving subcutaneous injection of carbon tetrachloride, a high-fat diet and 30 mL/L alcohol for 16 wk. At the fifth week, Yinshao powder or colchicine was intragastrically administered. After 12 wk of treatment, the rats were sacrificed to measure serum levels of hyaluronidase (HA), type Ⅳ collagen, procollagen type Ⅲ (PCⅢ), and laminin (LN), observe hepatic pathological changes by HE staining and Masson staining, and determine the mRNA and protein expression levels of TGF-β1 and β-catenin by RT-PCR and Western blot.

RESULTS: Compared with the colchicine group and model group, serum levels of HA, type Ⅳ collagen, PCⅢ, and LN declined significantly in the other groups. The degree of hepatic fibrosis in the Yinshao powder groups was less than that in the colchicine group and model group. The mRNA and protein expression levels of TGF-β1 and β-catenin were significantly lower in the Yinshao powder groups than in the model group and colchicine group.

CONCLUSION: Clearing heat, expelling damp and promoting blood circulation with Yinshao powder for intervention of hepatic fibrosis may be via molecular mechanisms associated with inhibiting or down-regulating the expression of TGF-β1 and β-catenin and blocking the activation of TGF-β1 signaling pathway and Wnt/β-catenin signaling pathway.

The WNT signaling pathway contributes to dectin-1-dependent inhibition of Toll-like receptor-induced inflammatory signature

Macrophages regulate cell fate decisions during microbial challenges by carefully titrating signaling events activated by innate receptors such as dectin-1 or Toll-like receptors (TLRs). Here, we demonstrate that dectin-1 activation robustly dampens TLR-induced proinflammatory signature in macrophages. Dectin-1 induced the stabilization of β-catenin via spleen tyrosine kinase (Syk)-reactive oxygen species (ROS) signals, contributing to the expression of WNT5A. Subsequently, WNT5A-responsive protein inhibitors of activated STAT (PIAS-1) and suppressor of cytokine signaling 1 (SOCS-1) mediate the downregulation of IRAK-1, IRAK-4, and MyD88, resulting in decreased expression of interleukin 12 (IL-12), IL-1β, and tumor necrosis factor alpha (TNF-α). In vivo activation of dectin-1 with pathogenic fungi or ligand resulted in an increased bacterial burden of Mycobacteria, Klebsiella, Staphylococcus, or Escherichia, with a concomitant decrease in TLR-triggered proinflammatory cytokines. All together, our study establishes a new role for dectin-1-responsive inhibitory mechanisms employed by virulent fungi to limit the proinflammatory environment of the host.

Regulation of activation and proliferation of hepatic stellate cells through the Wnt signaling pathway: Implications for treatment of liver fibrosis

Liver fibrosis, a reversible pathological condition occurring after chronic liver injury, is closely associated with the activation and proliferation of hepatic stellate cells (HSCs). Several studies have demonstrated that the Wnt signaling pathway is involved in the activation of HSCs, and then contributes to the occurrence and development of liver fibrosis. Thus, the Wnt signaling pathway and HSCs are considered to be the valid targets for the treatment of liver fibrosis. In recent years, domestic and international scholars have carried on many studies on the regulation of the Wnt signaling pathway and HSCs, trying to find out effective antifibrotic therapies. A large number of studies have shown that regulating HSCs can play a positive role in the treatment of liver fibrosis through the Wnt signaling pathway. On the basis of the relationship among the Wnt signaling pathway, HSCs and liver fibrosis, this review mainly summarizes the latest progress in the study of strategies for regulating HSCs through the Wnt signaling pathway and discusses the implications for the treatment of liver fibrosis.

Curcumin affects β-catenin pathway in hepatic stellate cell in vitro and in vivo

OBJECTIVES

Emerging evidence indicates that Wnt/β-catenin pathway is linked to the fibrosis of different organs including liver fibrosis. β-Catenin promotes hepatic stellate cells (HSCs) activation, a key event in the development of liver fibrosis, and has emerged as a novel mediator of fibrosis. Curcumin, a natural active ingredient derived from turmeric, possesses an inhibitory effect on liver fibrosis. This study is aimed to examine whether curcumin affects β-catenin expression/activity in HSCs and explores the underlying mechanisms.

METHODS

The researchers used Western blot, real-time PCR, transfection assay and electrophoretic mobility shift assay and employed cultured HSCs and rat model of liver injury.

KEY FINDINGS

Results showed that curcumin could reduce β-catenin protein level in HSCs in vitro and in vivo. Both β-catenin transactivation activity and DNA-binding activity were suppressed by curcumin. Moreover, nuclear β-catenin protein level was decreased by curcumin treatment. Further experiments suggested that delta-like homologue 1 contributed to curcumin inhibition of β-catenin transactivation activity in cultured HSCs.

CONCLUSIONS

Curcumin affects β-catenin pathway in HSCs and might suggest a possible new explanation for the effects of curcumin on HSC activation and liver fibrosis.