Switch from Mnt-Max to Myc-Max induces p53 and cyclin D1 expression and apoptosis during cholestasis in mouse and human hepatocytes

Swertia cincta and its main active ingredients regulate the PPAR-α pathway in anti-cholestatic liver injury

ETHNOPHARMACOLOGICAL RELEVANCE

Swertia cincta is a traditional remedy for cholestasis commonly utilised in Yunnan, China. Despite its widespread use, the specific active components and underlying mechanisms of action remain poorly understood.

AIM OF THIS STUDY

This study aimed to investigate the therapeutic properties, mechanisms, and active compounds of Swertia cincta in an animal model of cholestasis induced by alpha-naphthylisothiocyanate (ANIT).

MATERIALS AND METHODS

UHPLC/Q-TOF-MS and high-performance liquid chromatography (HPLC) were utilised to analyse the blood components of Swertia cincta. An ANIT-induced cholestatic liver injury animal model was established, and metabolomics was employed to explore the potential mechanisms of Swertia cincta in treating cholestatic liver injury. Hepatocellular injury induced by taurochenodeoxycholic acid was evaluated in vitro, and key bioactive components of Swertia cincta for cholestatic liver injury treatment were identified and confirmed using the ANIT-induced mouse model.

RESULTS

The established HPLC method demonstrates good specificity and reproducibility, enabling the simultaneous determination of six components in Swertia cincta. Results from serum biochemical indicators and liver pathology analysis indicated that Swertia cincta exhibits promising anti-cholestasis liver injury effects. Specifically, gentiopicroside, loganic acid, and isoorientin were identified as key active ingredients in treating cholestatic liver injury. Their mechanism of action primarily involves regulating PPAR-α, FXR, CYP3A4, NTCP, CAR, and CPT2. By modulating PPAR-α and bile acid metabolism-related proteins, reducing pro-inflammatory factors, enhancing bile acid transport, and promoting fatty acid oxidation to reduce lipid accumulation, Swertia cincta exerts protective and therapeutic effects against cholestatic liver injury. Notably, gentian bitter glycosides appear to be the most critical components for this effect.

CONCLUSION

Swertia cincta may improve cholestatic liver injury by activating the peroxisome proliferator-activated receptor alpha pathway, and the key active compounds were gentiopicroside, loganic acid, and isoorientin.

From regulation to deregulation of p53 in hematologic malignancies: implications for diagnosis, prognosis and therapy

The p53 protein, encoded by the TP53 gene, serves as a critical tumor suppressor, playing a vital role in maintaining genomic stability and regulating cellular responses to stress. Dysregulation of p53 is frequently observed in hematological malignancies, significantly impacting disease progression and patient outcomes. This review aims to examine the regulatory mechanisms of p53, the implications of TP53 mutations in various hematological cancers, and emerging therapeutic strategies targeting p53. We conducted a comprehensive literature review to synthesize recent findings related to p53's multifaceted role in hematologic cancers, focusing on its regulatory pathways and therapeutic potential. TP53 mutations in hematological malignancies often lead to treatment resistance and poor prognosis. Current therapeutic strategies, including p53 reactivation and gene therapy, show promise in improving treatment outcomes. Understanding the intricacies of p53 regulation and the consequences of its mutations is essential for developing effective diagnostic and therapeutic strategies in hematological malignancies, ultimately enhancing patient care and survival.

Pirfenidone ameliorates ANIT-induced cholestatic liver injury via modulation of FXR, NF-кB/TNF-α, and Wnt/GSK-3β/β-catenin signaling pathways

Cholestasis is a hepatobiliary disorder characterized by the excessive accumulation of toxic bile acids in hepatocytes, leading to cholestatic liver injury (CLI) through multiple pathogenic inflammatory pathways. Currently, there are limited therapeutic options for the management of cholestasis and associated CLI; therefore, new options are urgently needed. Pirfenidone (PF), an oral bioavailable pyridone analog, is used for the treatment of idiopathic pulmonary fibrosis. PF has recently demonstrated diverse potential therapeutic activities against different pathologies. Accordingly, the present study adopted the α-naphthyl isothiocyanate (ANIT)-induced CLI model in mice to explore the potential protective impact of PF and investigate the underlying mechanisms of action. PF intervention markedly reduced the serum levels of ALT, AST, LDH, total bilirubin, and total bile acids, which was accompanied by a remarkable amelioration of histopathological lesions induced by ANIT. PF also protected the mice against ANIT-induced redox imbalance in the liver, represented by reduced MDA levels and elevated GSH and SOD activities. Mechanistically, PF inhibited ANIT-induced downregulated expressions of the farnesoid X receptor (FXR), as well as the bile salt export pump (BSEP) and the multidrug resistance-associated protein 2 (MRP2) bile acid efflux channels. PF further repressed ANIT-induced NF-κB activation and TNF-α and IL-6 production. These beneficial effects were associated with its ability to dose-dependently inhibit Wnt/GSK-3β/β-catenin/cyclin D1 signaling. Collectively, PF protects against ANIT-induced CLI in mice, demonstrating powerful antioxidant and anti-inflammatory activities as well as an ability to oppose BA homeostasis disorder. These protective effects are primarily mediated by modulating the interplay between FXR, NF-κB/TNF-α/IL-6, and Wnt/β-catenin signaling pathways.

miR-194 Up-Regulates Cytochrome P450 Family 7 Subfamily A Member 1 Expression via β-Catenin Signaling and Aggravates Cholestatic Liver Diseases

miR-194 is abundantly expressed in hepatocytes, and its depletion induces hepatic resistance to acetaminophen-induced acute injuries. In this study, the biological role of miR-194 in cholestatic liver injury was investigated by using miR-194/miR-192 cluster liver-specific knockout (LKO) mice, in which no liver injuries or metabolic disorders were predisposed. Bile duct ligation (BDL) and 1-naphthyl isothiocyanate (ANIT) were applied to LKO and matched control wild-type (WT) mice to induce hepatic cholestasis. Periportal liver damage, mortality rate, and liver injury biomarkers in LKO mice were significantly less than in WT mice after BDL and ANIT injection. Intrahepatic bile acid level was significantly lower in the LKO liver within 48 hours of BDL- and ANIT-induced cholestasis compared with WT. Western blot analysis showed that β-catenin (CTNNB1) signaling and genes involved in cellular proliferation were activated in BDL- and ANIT-treated mice. The expression levels of cytochrome P450 family 7 subfamily A member 1 (CYP7A1), pivotal in bile synthesis, and its upstream regulator hepatocyte nuclear factor 4α were reduced in primary LKO hepatocytes and liver tissues compared with WT. The knockdown of miR-194 using antagomirs reduced CYP7A1 expression in WT hepatocytes. In contrast, the knockdown of CTNNB1 and overexpression of miR-194, but not miR-192, in LKO hepatocytes and AML12 cells increased CYP7A1 expression. In conclusion, the results suggest that the loss of miR-194 ameliorates cholestatic liver injury and may suppress CYP7A1 expression via activation of CTNNB1 signaling.

Serum microRNAs as non-invasive diagnostic biomarkers for intrahepatic cholestasis of pregnancy

OBJECTIVES

Intrahepatic cholestasis of pregnancy (IHCP) causes itching, preterm birth, and stillbirth. However, there is no accurate diagnostic method for IHCP. Currently, circulating microRNAs (miRNAs) have become candidate biomarkers for the diagnosis of multiple diseases. Here, we investigated the diagnostic value of miRNAs in IHCP and aimed to predict the molecular mechanism of IHCP pathogenesis.

METHODS

We analyzed differentially expressed miRNAs in both women with IHCP and normal pregnant women. The selected candidate miRNAs were validated in 46 IHCP cases and 46 normal pregnant subjects, and we constructed receiver operator characteristic curves of miRNAs. Pearson correlations between levels of total bile acid (TBA) and differentially expressed miRNAs were also calculated. In addition, we clustered functionally significant biological pathways using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses.

RESULTS

The expression levels of 13 miRNAs were remarkably upregulated while the other 35 miRNAs were significantly downregulated, in women with IHCP (P≤0.05) when compared with healthy pregnant women. The areas under the curves of miRNA-7706, miRNA-877-3p, and miRNA-128-3p were higher than 0.90, indicating more reliable diagnosis of IHCP. The Pearson analysis showed that the levels of these miRNAs were positively correlated to TBA level. Additionally, the results of bioinformatics analysis revealed that the differentially expressed miRNAs mainly influenced fatty acid biosynthesis, the endoplasmic reticulum ubiquitin ligase complex, and the p53, and mammalian target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK) signaling pathways.

CONCLUSION

The panel of three-miRNAs (miRNA-7706, miRNA-877-3p, and miRNA-128-3p) may be a useful noninvasive diagnostic biomarker of IHCP.

FTO Alleviates CdCl2-Induced Apoptosis and Oxidative Stress via the AKT/Nrf2 Pathway in Bovine Granulosa Cells

Cadmium (Cd) is a common environmental heavy metal contaminant of reproduction toxicity. Cd accumulation in animals leads to the damage of granulosa cells. However, its mechanism needs to be elucidated. This research found that treating granulosa cells with Cd resulted in reduced cell viability. The flow cytometry results showed that Cd increased the degree of apoptosis and level of superoxide anion (O₂^-) in granulosa cells. Further analysis showed that Cd treatment resulted in reduced expression levels of nuclear factor erythroid 2-related factor-2 (Nrf2), superoxide dismutase (SOD), catalase (CAT) and NAD(P)H: quinone oxidoreductase 1 (NQO1), and an increased expression level of malondialdehyde (MDA); the expression levels of Bcl-2 associated X (Bax) and caspase-3 increased, whereas that of B-cell lymphoma 2 (Bcl-2) decreased. Changes in m⁶A methylation-related enzymes were noted with Cd-induced damage to granulosa cells. The results of transcriptome and MeRIP sequencing revealed that the AKT pathway participated in Cd-induced damage in granulosa cells, and the MAX network transcriptional repressor (MNT) may be a potential target gene of fat mass and obesity-associated protein (FTO). FTO and YTH domain family member 2 (YTHDF2) regulated MNT expression through m⁶A modification. FTO overexpression alleviated Cd-induced apoptosis and oxidative stress through the activation of the AKT/Nrf2 pathway; this process could be reversed using siMNT. Overall, these findings associated m⁶A with Cd-induced damage to granulosa cells and provided insights into Cd-induced granulosa cell cytotoxicity from a new perspective centered on m⁶A modification.

Transcriptome analysis reveals the molecular mechanism of Yiqi Rougan decoction in reducing CCl4-induced liver fibrosis in rats

Background

Liver fibrosis develops from various chronic liver diseases, and there is currently a lack of specific treatment strategies. Yiqi Rougan decoction (YQRG) is a traditional Chinese medicine that has shown durative effects in the treatment of liver fibrosis; however, the mechanism associated with YQRG-related improvements in liver fibrosis remains to be experimentally determined. This study evaluated the therapeutic effect of YQRG on carbon tetrachloride (CCl₄)-induced liver fibrosis in rats and its molecular mechanism.

Methods

We used low-, medium-, and high-dose YQRG to treat CCl₄-induced liver fibrosis in rats, followed by assessment of liver injury and fibrosis according to liver appearance, body weight, liver mass index, histopathologic examination, and serum testing. Additionally, we performed transcriptome analysis using RNA-sequencing (RNA-seq) technology, including cluster, Gene Ontology (GO), and pathway analyses, to identify differentially expressed genes (DEGs), and protein and gene expression were detected by immunofluorescence (IFC), western blot and real-time quantitative PCR.

Results

The results showed that YQRG effectively alleviated CCl₄-induced liver injury and fibrosis in rats, including observations of improved liver function, decreased activity of hepatic stellate cells (HSCs), and decreased extracellular matrix (ECM) deposition. Moreover, we identified downregulated and upregulated DEGs in the model group relative to the control and YQRG-treated groups, with GO analysis revealing their enrichment in biological processes, such as endoplasmic reticulum stress (ERS), apoptosis, and autophagy. Furthermore, pathway analysis showed that YQRG treatment downregulated the mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase/Akt (PI3K/AKT) signalling pathways and upregulated other signalling pathways, including those related to peroxisome proliferator-activated receptors(PPAR) and AMP-activated protein kinase(AMPK), with these findings subsequently verified experimentally.

Conclusion

These findings showed that YQRG improved CCl₄-induced liver fibrosis through multiple mechanisms and pathways, offering critical insight into the YQRG-related therapeutic mechanism and promoting further research into its potential application.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13020-021-00552-w.

The Aged Intestine: Performance and Rejuvenation

Owing to the growing elderly population, age-related problems are gaining increasing attention from the scientific community. With senescence, the intestine undergoes a spectrum of changes and infirmities that are likely the causes of overall aging. Therefore, identification of the aged intestine and the search for novel strategies to rescue it, are required. Although progress has been made in research on some components of the aged intestine, such as intestinal stem cells, the comprehensive understanding of intestinal aging is still limited, and this restricts the in-depth search for efficient strategies. In this concise review, we discuss several aspects of intestinal aging. More emphasis is placed on the appraisal of current and potential strategies to alleviate intestinal aging, as well as future targets to rejuvenate the aged intestine.

The Multiple Faces of MNT and Its Role as a MYC Modulator

MNT is a crucial modulator of MYC, controls several cellular functions, and is activated in most human cancers. It is the largest, most divergent, and most ubiquitously expressed protein of the MXD family. MNT was first described as a MYC antagonist and tumor suppressor. Indeed, 10% of human tumors present deletions of one MNT allele. However, some reports show that MNT functions in cooperation with MYC by maintaining cell proliferation, promoting tumor cell survival, and supporting MYC-driven tumorigenesis in cellular and animal models. Although MAX was originally considered MNT's obligate partner, our recent findings demonstrate that MNT also works independently. MNT forms homodimers and interacts with proteins both outside and inside of the proximal MYC network. These complexes are involved in a wide array of cellular processes, from transcriptional repression via SIN3 to the modulation of metabolism through MLX as well as immunity and apoptosis via REL. In this review, we discuss the present knowledge of MNT with a special focus on its interactome, which sheds light on the complex and essential role of MNT in cell biology.

Interplay between nuclear factor erythroid 2-related factor 2 and inflammatory mediators in COVID-19-related liver injury

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 is a global pandemic and poses a major threat to human health worldwide. In addition to respiratory symptoms, COVID-19 is usually accompanied by systemic inflammation and liver damage in moderate and severe cases. Nuclear factor erythroid 2-related factor 2 (NRF2) is a transcription factor that regulates the expression of antioxidant proteins, participating in COVID-19-mediated inflammation and liver injury. Here, we show the novel reciprocal regulation between NRF2 and inflammatory mediators associated with COVID-19-related liver injury. Additionally, we describe some mechanisms and treatment strategies.

Reciprocal Regulation Between Forkhead Box M1/NF-κB and Methionine Adenosyltransferase 1A Drives Liver Cancer

BACKGROUND AND AIMS

Forkhead box M1 (FOXM1) and nuclear factor kappa B (NF-ĸB) are oncogenic drivers in liver cancer that positively regulate each other. We showed that methionine adenosyltransferase 1A (MAT1A) is a tumor suppressor in the liver and inhibits NF-ĸB activity. Here, we examined the interplay between FOXM1/NF-κB and MAT1A in liver cancer.

APPROACH AND RESULTS

We examined gene and protein expression, effects on promoter activities and binding of proteins to promoter regions, as well as effects of FOXM1 inhibitors T0901317 (T0) and forkhead domain inhibitory-6 (FDI-6) in vitro and in xenograft and syngeneic models of liver cancer. We found, in both hepatocellular carcinoma and cholangiocarcinoma, that an induction in FOXM1 and NF-κB expression is accompanied by a fall in MATα1 (protein encoded by MAT1A). The Cancer Genome Atlas data set confirmed the inverse correlation between FOXM1 and MAT1A. Interestingly, FOXM1 directly interacts with MATα1 and they negatively regulate each other. In contrast, FOXM1 positively regulates p50 and p65 expression through MATα1, given that the effect is lost in its absence. FOXM1, MATα1, and NF-κB all bind to the FOX binding sites in the FOXM1 and MAT1A promoters. However, binding of FOXM1 and NF-κB repressed MAT1A promoter activity, but activated the FOXM1 promoter. In contrast, binding of MATα1 repressed the FOXM1 promoter. MATα1 also binds and represses the NF-κB element in the presence of p65 or p50. Inhibiting FOXM1 with either T0 or FDI-6 inhibited liver cancer cell growth in vitro and in vivo. However, inhibiting FOXM1 had minimal effects in liver cancer cells that do not express MAT1A.

CONCLUSIONS

We have found a crosstalk between FOXM1/NF-κB and MAT1A. Up-regulation in FOXM1 lowers MAT1A, but raises NF-κB, expression, and this is a feed-forward loop that enhances tumorigenesis.

Anticancer Effect of Radix Astragali on Cholangiocarcinoma In Vitro and Its Mechanism via Network Pharmacology

Background

This study used network pharmacology method and cell model to assess the effects of Radix Astragali (RA) on cholangiocarcinoma (CCA) and to predict core targets and molecular mechanisms.

Material/Methods

We performed an in vitro study to assess the effect of RA on CCA using CCK8 assay, the Live-Cell Analysis System, and trypan blue staining. The components and targets of RA were analyzed using the Traditional Chinese Medicine Systems Pharmacology database, and genes associated with CCA were retrieved from the GeneCards and OMIM platforms. Protein–protein interactions were analyzed with the STRING platform. The components–targets–disease network was built by Cytoscape. The TIMER database revealed the expression of core targets with diverse immune infiltration levels. GO and KEGG analyses were performed to identify molecular-biology processes and signaling pathways. The predictions were verified by Western blotting.

Results

Concentration-dependent antitumor activity was confirmed in the cholangiocarcinoma QBC939 cell line treated with RA. RA contained 16 active compounds, with quercetin and kaempferol as the core compounds. The most important biotargets for RA in CCA were caspase 3, MAPK8, MYC, EGFR, and PARP. The TIMER database revealed that the expression of caspase3 and MYC was related with diverse immune infiltration levels of CCA. The results of Western blotting showed RA significantly influenced the expression of the 5 targets that network pharmacology predicted.

Conclusions

RA is an active medicinal material that can be developed into a safe and effective multi-targeted anticancer treatment for CCA.

Hepatocyte-derived exosomal MiR-194 activates PMVECs and promotes angiogenesis in hepatopulmonary syndrome

Hepatopulmonary syndrome (HPS) is a serious vascular complication in the setting of liver disease. Factors produced by the liver are essential to regulate pulmonary angiogenesis in the pathogenesis of HPS; however, the pathogenic mechanisms of pulmonary angiogenesis are not fully understood. We investigated the role of HPS rat serum exosomes (HEs) and sham-operated rat serum exosomes (SEs) in the regulation of angiogenesis. We found that HEs significantly enhance PMVEC proliferation, migration, and tube formation. We further identified miR-194 was the most notably increased miRNA in HEs compared to SEs. Once released, hepatocyte-derived exosomal miR-194 was internalized by PMVECs, leading to the promotion of PMVEC proliferation, migration, and tube formation through direct targeting of THBS1, STAT1, and LIF. Importantly, the pathogenic role of exosomal miR-194 in initiating angiogenesis was reversed by P53 inhibition, exosome secretion inhibition or miR-194 inhibition. Additionally, high levels of miR-194 were found in serum exosomes and were positively correlated with P(A-a)O₂ in HPS patients and rats. Thus, our results highlight that the exosome/miR-194 axis plays a critical pathologic role in pulmonary angiogenesis, representing a new therapeutic target for HPS.

Krüppel-like factor 6 mediates pulmonary angiogenesis in rat experimental hepatopulmonary syndrome and is aggravated by bone morphogenetic protein 9

Hepatopulmonary syndrome (HPS) is a serious pulmonary vascular disease derived from chronic liver disease, and its key pathogenesis is angiogenesis. Krüppel-like factor 6 (KLF6) mediates physiological repair and remodeling during vascular injury. However, the role of KLF6 in pulmonary microvascular endothelial cells (PMVECs) during angiogenesis of HPS and its underlying mechanism in HPS have not been investigated. Common bile duct ligation (CBDL) in rats can replicate pulmonary vascular abnormalities of human HPS. Here, we found that advanced pulmonary angiogenesis and pulmonary injury score coincided with the increase of KLF6 level in PMVECs of CBDL rat; KLF6 in PMVECs was also induced while cultured with CBDL rat serum in vitro. Inhibition of KLF6 dramatically suppressed PMVEC-mediated proliferation, migration and tube formation in vivo; this may be related to the downregulation of activin receptor-like kinase-1 (ALK1) and endoglin (ENG), which are transacted by KLF6. Bone morphogenetic protein 9 (BMP9) enhanced the expression of KLF6 in PMVECs and was involved in the angiogenesis of HPS. These results suggest that KLF6 triggers PMVEC-mediated angiogenesis of HPS and is aggravated by BMP9, and the inhibition of the BMP9/KLF6 axis may be an effective strategy for HPS treatment.

Summary: Krüppel-like factor 6, which is triggered by pulmonary injury and promoted by bone morphogenetic protein 9, mediates pulmonary angiogenesis in rat experimental hepatopulmonary syndrome and then aggravates lung dysfunction.

Bioinformatics‑based identification of key pathways and candidate genes for estrogen‑induced intrahepatic cholestasis using DNA microarray analysis

Estrogen‑induced intrahepatic cholestasis (EIC) has increased incidence during pregnancy, and within women taking oral contraception and postmenopausal hormone replacement therapy. However, the pathology underlying EIC is not well understood. The aim of the present study was to identify key pathways and candidate genes in estrogen‑induced intrahepatic cholestasis (EIC) that may be potential targets for diagnosis and treatment. A whole‑genome microarray (4x44K) analysis of a 17α‑ethinylestradiol (EE)‑induced EIC rat liver model was performed. Bioinformatics‑based methods were used to identify key pathways and candidate genes associated with EIC. The candidate genes were validated using a reverse transcription quantitative polymerase chain reaction assay. A total of 455 genes were differentially expressed (P<0.05 and fold change >2.0) following EE treatment, including 225 downregulated genes and 230 upregulated genes. Sulfotransferase family 1E member 1, cytochrome P450 family 3 subfamily A member 2, carbonic anhydrase 3, leukotriene C4 synthase and ADAM metallopeptidase domain 8 were the 5 candidate genes identified to be differentially expressed and involved in the metabolism of estrogens and bile acids and the regulation of inflammation and oxidative stress. The Analyses of Gene Ontology enrichment, Kyoto Encyclopedia of Genes and Genomes pathways and protein‑protein interaction network associated‑modules identified several key pathways involved in the homeostasis of lipids and bile acids and in AMPK, p53 and Wnt signaling. These key pathways and candidate genes may have critical roles in the pathogenesis of EIC. In addition, reversing the abnormal expression of candidate genes or restoring the dysfunction of key pathways may provide therapeutic opportunities for patients with EIC.

Metabolic Reprogramming and the Recovery of Physiological Functionality in 3D Cultures in Micro-Bioreactors

The recovery of physiological functionality, which is commonly seen in tissue mimetic three-dimensional (3D) cellular aggregates (organoids, spheroids, acini, etc.), has been observed in cells of many origins (primary tissues, embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), and immortal cell lines). This plurality and plasticity suggest that probably several basic principles promote this recovery process. The aim of this study was to identify these basic principles and describe how they are regulated so that they can be taken in consideration when micro-bioreactors are designed. Here, we provide evidence that one of these basic principles is hypoxia, which is a natural consequence of multicellular structures grown in microgravity cultures. Hypoxia drives a partial metabolic reprogramming to aerobic glycolysis and an increased anabolic synthesis. A second principle is the activation of cytoplasmic glutaminolysis for lipogenesis. Glutaminolysis is activated in the presence of hypo- or normo-glycaemic conditions and in turn is geared to the hexosamine pathway. The reducing power needed is produced in the pentose phosphate pathway, a prime function of glucose metabolism. Cytoskeletal reconstruction, histone modification, and the recovery of the physiological phenotype can all be traced to adaptive changes in the underlying cellular metabolism. These changes are coordinated by mTOR/Akt, p53 and non-canonical Wnt signaling pathways, while myc and NF-kB appear to be relatively inactive. Partial metabolic reprogramming to aerobic glycolysis, originally described by Warburg, is independent of the cell’s rate of proliferation, but is interwoven with the cells abilities to execute advanced functionality needed for replicating the tissues physiological performance.

p63α modulates c-Myc activity via direct interaction and regulation of MM1 protein stability

Both p53-related p63 and c-Myc are transcription factors playing key roles in cell proliferation, survival, development and tumorigenesis. In the present study, we identified that MM1, a c-Myc inhibitor, specifically binds to C-termini of p63α (including ΔNp63α and TAp63α). Further study demonstrates that p63α facilitates MM1 protein degradation via proteasomal pathway, resulting in elevation of c-Myc transactivation activity. Knockdown of ΔNp63α leads to decrease in c-Myc protein levels, concomitant with reduced expression of CDK4 and Cyclin D1, and impaired cell cycle progression, both of which are effectively reversed by simultaneous knockdown of MM1. Moreover, expression of p63 and CDK4 is concomitantly up-regulated in B-cell acute lymphoblastic leukemia. Together, this study reveals a novel crosstalk between p63 and c-Myc that may play an important role in cell cycle progression and tumorigenesis.

p53-mediated regulation of bile acid disposition attenuates cholic acid-induced cholestasis in mice

BACKGROUND AND PURPOSE

The tumour suppressor p53 is traditionally recognized as a surveillance molecule to preserve genome integrity. Recent studies have demonstrated that it contributes to metabolic diseases. Here, we investigated the role of p53 in the regulation of bile acid disposition and cholestasis.

EXPERIMENTAL APPROACH

The bile acid disposition-related gene expression profile affected by p53 activation was assessed in mouse primary hepatocytes with p53 depletion and in Trp53-null mice. Dual luciferase reporter assay was used to detect the transcriptional activities of target genes. Anticholestatic effects of p53 activator doxorubicin were investigated in a 0.5% cholic acid-fed mouse model of cholestasis. Changes in bile acids were evaluated using metabolomics analysis.

KEY RESULTS

Doxorubicin-mediated p53 activation induced Cyp2b10, Sult2a1 and Abcc2/3/4 expression in mice in vitro and in vivo. ABCC3 and CYP2B6 (human orthologue of Cyp2b10) were identified as direct p53 target genes. Doxorubicin attenuated cholic acid-induced cholestasis in mice, as demonstrated by shrunken gall bladder, decreased serum total bile acid and total bilirubin levels and alkaline phosphatase activity. Targeted metabolomics analysis revealed that doxorubicin enhanced the excretion of bile acid metabolites from serum and liver to intestine and faeces. Up-regulation of Cyp2b10, Sult2a1 and Abcc2/3/4 expression was further confirmed in cholestatic mice. Cholic acid-induced cholestatic injury was aggravated in p53-deficient mice and levels of bile acid in intestine and faeces were decreased.

CONCLUSIONS AND IMPLICATIONS

Our findings suggest a novel role of p53 in promoting bile acid disposition and alleviating cholestatic syndrome, which provides a potential therapeutic target for cholestasis.

c‑Myc promotes cholangiocarcinoma cells to overcome contact inhibition via the mTOR pathway

The loss of contact inhibition is a hallmark of a wide range of human cancer cells. Yet, the precise mechanism behind this process is not fully understood. c‑Myc plays a pivotal role in carcinogenesis, but its involvement in regulating contact inhibition has not been explored to date. Here, we report that c‑Myc plays an important role in abrogating contact inhibition in human cholangiocarcinoma (CCA) cells. Our data show that the protein level of c‑Myc obviously decreased in contact-inhibited normal biliary epithelial cells. However, CCA cells sustain high protein levels of c‑Myc and keep strong proliferation ability in confluent conditions. Importantly, the suppression of c‑Myc by inhibitor or siRNA induced G0/G1 phase cell cycle arrest in confluent CCA cells. We demonstrate that the inhibition of c‑Myc suppressed the activity of mammalian target of rapamycin (mTOR) in confluent CCA cells, and mTOR inhibition induced G0/G1 phase cell cycle arrest in confluent CCA cells. In confluent CCA cells, the activity of Merlin is downregulated, and Yes-associated protein (YAP) sustains high levels of activity. Furthermore, YAP inhibition not only induced G0/G1 phase cell cycle arrest, but also decreased c‑Myc expression in confluent CCA cells. These results indicate that Merlin/YAP/c‑Myc/mTOR signaling axis promotes human CCA cell proliferation by overriding contact inhibition. We propose that overriding c‑Myc‑mediated contact inhibition is implicated in the development of CCA.

c-MYC-Making Liver Sick: Role of c-MYC in Hepatic Cell Function, Homeostasis and Disease

Over 35 years ago, c-MYC, a highly pleiotropic transcription factor that regulates hepatic cell function, was identified. In recent years, a considerable increment in the number of publications has significantly shifted the way that the c-MYC function is perceived. Overexpression of c-MYC alters a wide range of roles including cell proliferation, growth, metabolism, DNA replication, cell cycle progression, cell adhesion and differentiation. The purpose of this review is to broaden the understanding of the general functions of c-MYC, to focus on c-MYC-driven pathogenesis in the liver, explain its mode of action under basal conditions and during disease, and discuss efforts to target c-MYC as a plausible therapy for liver disease.

MNT and Emerging Concepts of MNT-MYC Antagonism

MYC family proteins play fundamental roles in stem and progenitor cell homeostasis, morphogenesis and cancer. As expected for proteins that profoundly affect the fate of cells, the activities of MYC are regulated at a multitude of levels. One mechanism with the potential to broadly affect the activities of MYC is transcriptional antagonism by a group of MYC-related transcriptional repressors. From this group, the protein MNT has emerged as having perhaps the most far-reaching impact on MYC activities. In this review, we discuss the current understanding of MNT, its regulation and how, as a MYC antagonist, it functions both as a tumor suppressor and facilitator of MYC-driven proliferation and oncogenesis.

E3 ubiquitin ligase FBW7α inhibits cholangiocarcinoma cell proliferation by downregulating c-Myc and cyclin E

FBW7 (F-box and WD repeat domain-containing 7), also known as CDC4, AGO and SEL10, is the substrate recognition component of an evolutionary conserved SCF (complex of SKP1, CUL1 and F-box protein)-type E3 ubiquitin ligase. It is a recognized tumor suppressor because it targets multiple oncoproteins for ubiquitination-mediated destruction and its mutations are frequently identified in a variety of human malignancies. However, the function of FBW7 in proliferation of cholangiocarcinoma (CCA) remains unknown. We found that overexpression of FBW7α induced CCA cell arrest in G1 phase of cell cycle and inhibited cell proliferation in vitro and CCA xenograft tumor growth, suggesting that FBW7α is a tumor suppressor in CCA progression. Overxpression of FBW7α resulted in the protein degradation of its substrates such as c-Myc and cyclin E which promote CCA cell proliferation. Restoration of the expression of c-Myc, but not cyclin E, rescued the proliferation of FBW7α-overexpression CCA cells. These results suggest that FBW7α plays an essential inhibitory role in CCA progression, indicating that targeting FBW7α substrate c-Myc may be a potential strategy for CCA treatment.

Modulation of the Unfolded Protein Response by Tauroursodeoxycholic Acid Counteracts Apoptotic Cell Death and Fibrosis in a Mouse Model for Secondary Biliary Liver Fibrosis

The role of endoplasmic reticulum stress and the unfolded protein response (UPR) in cholestatic liver disease and fibrosis is not fully unraveled. Tauroursodeoxycholic acid (TUDCA), a hydrophilic bile acid, has been shown to reduce endoplasmic reticulum (ER) stress and counteract apoptosis in different pathologies. We aimed to investigate the therapeutic potential of TUDCA in experimental secondary biliary liver fibrosis in mice, induced by common bile duct ligation. The kinetics of the hepatic UPR and apoptosis during the development of biliary fibrosis was studied by measuring markers at six different timepoints post-surgery by qPCR and Western blot. Next, we investigated the therapeutic potential of TUDCA, 10 mg/kg/day in drinking water, on liver damage (AST/ALT levels) and fibrosis (Sirius red-staining), in both a preventive and therapeutic setting. Common bile duct ligation resulted in the increased protein expression of CCAAT/enhancer-binding protein homologous protein (CHOP) at all timepoints, along with upregulation of pro-apoptotic caspase 3 and 12, tumor necrosis factor receptor superfamily, member 1A (TNFRsf1a) and Fas-Associated protein with Death Domain (FADD) expression. Treatment with TUDCA led to a significant reduction of liver fibrosis, accompanied by a slight reduction of liver damage, decreased hepatic protein expression of CHOP and reduced gene and protein expression of pro-apoptotic markers. These data indicate that TUDCA exerts a beneficial effect on liver fibrosis in a model of cholestatic liver disease, and suggest that this effect might, at least in part, be attributed to decreased hepatic UPR signaling and apoptotic cell death.

Hypoxia-inducible factor-2α promotes hepatocyte apoptosis during cholestasis

AIM

Hypoxia-inducible factor-2α (HIF-2α) has been reported to play an important role in a host of pathophysiological processes, including cellular survival. This study explores the role of HIF-2α in cholestasis-mediated hepatocyte apoptosis.

METHODS

Hypoxia-inducible factor-2α expression was measured by immunohistochemistry and confocal microscopy. Hepatic apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick-end labeling. The cholestatic mouse model was treated with bile duct ligation. The c-myc, p53, and Bax protein levels were measured with Western blot analysis.

RESULTS

In pediatric and murine cholestatic liver tissues, HIF-2α protein was widely expressed in the nucleus of parenchymal cells as well as in stromal cells. Hepatocyte HIF-2α expression was significantly elevated at the early stage of pediatric cholestasis and decreased at the late stage. In both in vivo and in vitro murine studies, HIF-2α deletion could alleviate cholestasis-mediated hepatocyte apoptosis and regulate the expression of c-myc, p53, and Bax proteins.

CONCLUSION

These findings implied the contribution of HIF-2α to cholestasis-mediated hepatocyte apoptosis.

MicroRNA-mediated regulation of glutathione and methionine metabolism and its relevance for liver disease

The discovery of the microRNA (miRNA) family of small RNAs as fundamental regulators of post-transcriptional gene expression has fostered research on their importance in every area of biology and clinical medicine. In the particular area of liver metabolism and disease, miRNAs are gaining increasing importance. By focusing on two fundamental hepatic biosynthetic pathways, glutathione and methionine, we review recent advances on the comprehension of the role of miRNAs in liver pathophysiology and more specifically of models of hepatic cholestasis/fibrosis and hepatocellular carcinoma.

AP-1 Inhibition by SR 11302 Protects Human Hepatoma HepG2 Cells from Bile Acid-Induced Cytotoxicity by Restoring the NOS-3 Expression

The harmful effects of bile acid accumulation occurring during cholestatic liver diseases have been associated with oxidative stress increase and endothelial nitric oxide synthase (NOS-3) expression decrease in liver cells. We have previously reported that glycochenodeoxycholic acid (GCDCA) down-regulates gene expression by increasing SP1 binding to the NOS-3 promoter in an oxidative stress dependent manner. In the present study, we aimed to investigate the role of transcription factor (TF) AP-1 on the NOS-3 deregulation during GCDCA-induced cholestasis. The cytotoxic response to GCDCA was characterized by 1) the increased expression and activation of TFs cJun and c-Fos; 2) a higher binding capability of these at position -666 of the NOS-3 promoter; 3) a decrease of the transcriptional activity of the promoter and the expression and activity of NOS-3; and 4) the expression increase of cyclin D1. Specific inhibition of AP-1 by the retinoid SR 11302 counteracted the cytotoxic effects induced by GCDCA while promoting NOS-3 expression recovery and cyclin D1 reduction. NOS activity inhibition by L-NAME inhibited the protective effect of SR 11302. Inducible NOS isoform was no detected in this experimental model of cholestasis. Our data provide direct evidence for the involvement of AP-1 in the NOS-3 expression regulation during cholestasis and define a critical role for NOS-3 in regulating the expression of cyclin D1 during the cell damage induced by bile acids. AP-1 appears as a potential therapeutic target in cholestatic liver diseases given its role as a transcriptional repressor of NOS-3.

Deregulated methionine adenosyltransferase α1, c-Myc, and Maf proteins together promote cholangiocarcinoma growth in mice and humans(‡)

c-Myc induction drives cholestatic liver injury and cholangiocarcinoma (CCA) in mice, and induction of Maf proteins (MafG and c-Maf) contributes to cholestatic liver injury, whereas S-adenosylmethionine (SAMe) administration is protective. Here, we determined whether there is interplay between c-Myc, Maf proteins, and methionine adenosyltransferase α1 (MATα1), which is responsible for SAMe biosynthesis in the liver. We used bile duct ligation (BDL) and lithocholic acid (LCA) treatment in mice as chronic cholestasis models, a murine CCA model, human CCA cell lines KMCH and Huh-28, human liver cancer HepG2, and human CCA specimens to study gene and protein expression, protein-protein interactions, molecular mechanisms, and functional outcomes. We found that c-Myc, MATα1 (encoded by MAT1A), MafG, and c-Maf interact with one another directly. MAT1A expression fell in hepatocytes and bile duct epithelial cells during chronic cholestasis and in murine and human CCA. The opposite occurred with c-Myc, MafG, and c-Maf expression. MATα1 interacts mainly with Mnt in normal liver, but this switches to c-Maf, MafG, and c-Myc in cholestatic livers and CCA. Promoter regions of these genes have E-boxes that are bound by MATα1 and Mnt in normal liver and benign bile duct epithelial cells that switched to c-Myc, c-Maf, and MafG in cholestasis and CCA cells. E-box positively regulates c-Myc, MafG, and c-Maf, but it negatively regulates MAT1A. MATα1 represses, whereas c-Myc, MafG, and c-Maf enhance, E-box-driven promoter activity. Knocking down MAT1A or overexpressing MafG or c-Maf enhanced CCA growth and invasion in vivo.

CONCLUSION

There is a novel interplay between MATα1, c-Myc, and Maf proteins, and their deregulation during chronic cholestasis may facilitate CCA oncogenesis. (Hepatology 2016;64:439-455).

RNAi-nanoparticulate manipulation of gene expression as a new functional genomics tool in the liver

BACKGROUND & AIMS

The Hippo pathway controls organ size through a negative regulation of the transcription co-activator Yap1. The overexpression of hyperactive mutant Yap1 or deletion of key components in the Hippo pathway leads to increased organ size in different species. Analysis of interactions of this pathway with other cellular signals corroborating organ size control is limited in part due to the difficulties associated with development of rodent models.

METHODS

Here, we develop a new model of reversible induction of the liver size in mice using siRNA-nanoparticles targeting two kinases of the Hippo pathway, namely, mammalian Ste20 family kinases 1 and 2 (Mst1 and Mst2), and an upstream regulator, neurofibromatosis type II (Nf2).

RESULTS

The triple siRNAs nanoparticle-induced hepatomegaly in mice phenocopies one observed with Mst1(-/-)Mst2(-/-) liver-specific depletion, as shown by extensive proliferation of hepatocytes and activation of Yap1. The simultaneous co-treatment with a fourth siRNA nanoparticle against Yap1 fully blocked the liver growth. Hippo pathway-induced liver enlargement is associated with p53 activation, evidenced by its accumulation in the nuclei and upregulation of its target genes. Moreover, injections of the triple siRNAs nanoparticle in p53(LSL/LSL) mice shows that livers lacking p53 expression grow faster and exceed the size of livers in p53 wild-type animals, indicating a role of p53 in controlling Yap1-induced liver growth.

CONCLUSION

Our data show that siRNA-nanoparticulate manipulation of gene expression can provide the reversible control of organ size in adult animals, which presents a new avenue for the investigation of complex regulatory networks in liver.

The role of miRNAs in cholangiocarcinoma

Cholangiocarcinoma (CCA) is a devastating malignancy with high mortality, in part due to the combination of late presentation, significant diagnostic challenges and limited effective treatment options. Late presentation and diagnosis contribute to the high mortality in CCA and there is an urgent unmet need for diagnostic and prognostic biomarkers to facilitate early diagnosis and treatment stratification to improve clinical outcomes. MiRs are small ncRNA molecules that regulate gene expression and modulate both tumor suppressive and oncogenic pathways. They have a well-defined role in carcinogenesis, including CCA. In this review, we outline the evidence for MiRs in the pathogenesis of CCA and their potential utility as diagnostic and prognostic biomarkers to guide clinical management.

Integrin α1β1 expression is controlled by c-MYC in colorectal cancer cells

The α1β1 collagen receptor is only present in a few epithelial cell types. In the intestine, it is specifically expressed in proliferating crypt cells. This integrin has been reported to be involved in various cancers where it mediates the downstream activation of the Ras/ERK proliferative pathway. We have recently shown that integrin α1β1 is present in two-thirds of colon adenocarcinomas, but the mechanism by which ITGA1 expression is regulated is not known. DNA methylation, involved in ITGA1 repression during megakaryocyte differentiation, is not the mechanism of ITGA1 regulation in colorectal cancer cells. Our in silico analysis of the ITGA1 promoter revealed two response elements for MYC, an oncogenic factor known to regulate cancer cell proliferation, invasion and migration. In situ, the expressions of both MYC and ITGA1 are localized in the lower crypt of the normal colon and correlate in 72% of the 65 analyzed colorectal cancers. MYC pharmacological inhibition or downregulation of expression with short hairpin RNA in HT29, T84 and SW480 cells resulted in reduced ITGA1 expression at both the transcript and protein levels. Chromatin immunoprecipitation assays revealed that MYC was bound to the chromatin region of the ITGA1 proximal promoter, whereas MYC overexpression enhanced ITGA1 promoter activity that was reduced with MAD co-transfection or by the disruption of the response elements. We concluded that MYC is a key regulating factor for the control of ITGA1 expression.

Interactions between Myc and Mediators of Inflammation in Chronic Liver Diseases

Most chronic liver diseases (CLDs) are characterized by inflammatory processes with aberrant expressions of various pro- and anti-inflammatory mediators in the liver. These mediators are the driving force of many inflammatory liver disorders, which often result in fibrosis, cirrhosis, and liver tumorigenesis. c-Myc is involved in many cellular events such as cell growth, proliferation, and differentiation. c-Myc upregulates IL-8, IL-10, TNF-α, and TGF-β, while IL-1, IL-2, IL-4, TNF-α, and TGF-β promote c-Myc expression. Their interactions play a central role in fibrosis, cirrhosis, and liver cancer. Molecular interference of their interactions offers possible therapeutic potential for CLDs. In this review, current knowledge of the molecular interactions between c-Myc and various well known inflammatory mediators is discussed.

In vitro antiproliferative and antioxidant effects of urolithin A, the colonic metabolite of ellagic acid, on hepatocellular carcinomas HepG2 cells

The intestinal metabolites of ellagic acid (EA), urolithins are known to effectively inhibit cancer cell proliferation. This study investigates antiproliferative and antioxidant effects of urolithin A (UA) on cell survival of the HepG2 hepatic carcinomas cell line. The antiproliferative effects of UA (0-500 μM) on HepG2 cells were determined using a CCK assay following 12-36 h exposure. Effects on β-catenin and other factors of expression were assessed by using real-time PCR and Western blot. We found that UA showed potent antiproliferative activity on HepG2 cells. When cell death was induced by UA, it was found that the expression of β-catenin, c-Myc and Cyclin D1 were decreased and TCF/LEF transcriptional activation was notably down-regulated. UA also increased protein expression of p53, p38-MAPK and caspase-3, but suppressed expression of NF-κB p65 and other inflammatory mediators. Furthermore, the antioxidant assay afforded by UA and EA treatments was associated with decreases in intracellular ROS levels, and increases in intracellular SOD and GSH-Px activity. These results suggested that UA could inhibit cell proliferation and reduce oxidative stress status in liver cancer, thus acting as a viably effective constituent for HCC prevention and treatment.

Caspase-3 inhibition prevents the development of hepatopulmonary syndrome in common bile duct ligation rats by alleviating pulmonary injury

BACKGROUND & AIMS

Common bile duct ligation (CBDL) rats is an accepted experimental model of hepatopulmonary syndrome (HPS), defined as liver disease and intrapulmonary vascular dilatation and hypoxaemia. Pulmonary Akt and ERK activation followed by angiogenesis in the later stages of CBDL, contribute to the pathogenesis of HPS. However, the mechanisms behind Akt and ERK activation remain undefined. Pulmonary injury induced by increased bilirubin, endotoxin and inflammatory mediators occurs in the early stages of CBDL. We assessed the effects of relieving pulmonary injury on Akt and ERK activation and on the development of HPS following CBDL.

METHODS

Pulmonary injury, angiogenesis, arterial oxygenation, cell proliferation and, phospho-Akt and ERK1 were evaluated in CBDL animals with or without caspase-3 inhibition (Z-DEVD-FMK). Pulmonary injury was assessed by histology and quantifying apoptosis and aquaporin-1 (AQP1) levels. Lung angiogenesis was assessed by quantifying AQP1 level, vWF-positive cells and microvessel count.

RESULTS

Pulmonary apoptosis and caspase-3 activation were markedly increased in the early stages of CBDL. Caspase-3 inhibition alleviated apoptosis, the reduction in AQP1, phospho-Akt and ERK1 levels and pulmonary injury 1 week after CBDL. Caspase-3 inhibition also reduced AQP1, phospho-Akt and ERK1 levels, vWF-positive cells, cell proliferation, microvessel count, and microvascular dilatation and improved arterial oxygenation 3 weeks following CBDL.

CONCLUSIONS

Caspase-3 inhibition alleviates pulmonary injury, thereby preventing angiogenesis as well as the development of HPS in CBDL rats. These effects are related to the regulation of the Akt and ERK1 pathways.

Activation of a novel c-Myc-miR27-prohibitin 1 circuitry in cholestatic liver injury inhibits glutathione synthesis in mice

AIMS

We showed that chronic cholestatic liver injury induced the expression of c-Myc but suppressed that of glutamate-cysteine ligase (GCL, composed of catalytic and modifier subunits GCLC and GCLM, respectively). This was associated with reduced nuclear antioxidant response element (ARE) binding by nuclear factor-erythroid 2 related factor 2 (Nrf2). Here, we examined whether c-Myc is involved in this process.

RESULTS

Similar to bile duct ligation (BDL), lithocholic acid (LCA) treatment in vivo induced c-Myc but suppressed GCL subunits expression at day 14. Nrf2 expression and Nrf2 ARE binding fell markedly. However, Nrf2 heterodimerization with MafG was enhanced by LCA, which prompted us to examine whether LCA treatment in vivo altered proteins that bind to ARE using biotinylated ARE in pull-down assay followed by proteomics. LCA treatment enhanced c-Myc but lowered prohibitin 1 (PHB1) binding to ARE. This was a result of c-Myc-mediated induction of microRNA 27a/b (miR27a/b), which target both PHB1 and Nrf2 to reduce their expression. Knockdown of c-Myc or miR27a/b attenuated LCA-mediated suppression of Nrf2, PHB1, and GCL subunit expression, whereas overexpression of PHB1 protected against the fall in Nrf2 and GCL subunits. Both c-Myc and PHB1 directly interact with Nrf2 but c-Myc lowers Nrf2 binding to ARE while PHB1 enhances it.

INNOVATION

This is the first work that shows how activation of this circuit in cholestatic liver injury inhibits GCL expression.

CONCLUSIONS

LCA feeding and BDL activate c-Myc-miR27a/b-PHB1 circuit, with the consequence of inhibiting Nrf2 expression and ARE binding, resulting in decreased reduced glutathione synthesis and antioxidant capacity.

p53 promotes inflammation-associated hepatocarcinogenesis by inducing HMGB1 release

BACKGROUND & AIMS

Hepatocellular carcinoma (HCC) develops in response to chronic hepatic injury. Although induced cell death is regarded as the major component of p53 tumor-suppressive activity, we recently found that sustained p53 activation subsequent to DNA damage promotes inflammation-associated hepatocarcinogenesis. Here we aim at exploring the mechanism linking p53 activation and hepatic inflammation during hepatocarcinogenesis.

METHODS

p53(-/-) hepatocytes expressing inducible p53 and primary wild type hepatocytes were treated to induce p53 expression. The supernatants were collected and analyzed for the presence of released inflammatory cytokines. Ethyl pyruvate was used in a rat model of carcinogen-induced hepatocarcinogenesis to examine its effect on p53-dependent chronic hepatic injury, inflammation, and tumorigenesis.

RESULTS

Here we show that cytoplasmic translocation and circulating levels of potent inflammatory molecule high-mobility group protein 1 (HMGB1) were greater in wild type rats than in p53(+/-) rats following carcinogen administration. Restoration of p53 expression in p53-null hepatocytes or induction of endogenous p53 in wild type hepatocytes gives rise to the release of HMGB1. Administration of the HMGB1 release inhibitor ethyl pyruvate, which does not affect p53-mediated hepatic apoptosis, substantially prevented carcinogen-induced cirrhosis and tumorigenesis in rat livers.

CONCLUSIONS

These results suggest that although p53 is usually regarded as a tumor suppressor, its constant activation can promote pro-tumorigenic inflammation, at least in part, via inducing HMGB1 release. Application of HMGB1 inhibitors when restoring p53 in cancer therapy might protect against pro-tumorigenic effects while leaving p53-mediated clearance of malignant cells intact.

Bile acids induce apoptosis selectively in androgen-dependent and -independent prostate cancer cells

Prostate cancer is a prevalent age-related disease in North America, accounting for about 15% of all diagnosed cancers. We have previously identified lithocholic acid (LCA) as a potential chemotherapeutic compound that selectively kills neuroblastoma cells while sparing normal human neurons. Now, we report that LCA inhibits the proliferation of androgen-dependent (AD) LNCaP prostate cancer cells and that LCA is the most potent bile acid with respect to inducing apoptosis in LNCaP as well as androgen-independent (AI) PC-3 cells, without killing RWPE-1 immortalized normal prostate epithelial cells. In LNCaP and PC-3 cells, LCA triggered the extrinsic pathway of apoptosis and cell death induced by LCA was partially dependent on the activation of caspase-8 and -3. Moreover, LCA increased cleavage of Bid and Bax, down-regulation of Bcl-2, permeabilization of the mitochondrial outer membrane and activation of caspase-9. The cytotoxic actions of LCA occurred despite the inability of this bile acid to enter the prostate cancer cells with about 98% of the nominal test concentrations present in the extracellular culture medium. With our findings, we provide evidence to support a mechanism of action underlying the broad anticancer activity of LCA in various human tissues.

Animal models of cholangiocarcinoma

PURPOSE OF REVIEW

Even though recent accumulated data can help to understand fundamental molecular mechanisms of progression of cholangiocarcinoma (CCA), its incidence and mortality still keep increasing worldwide with poor prognosis. As appropriate animal disease models are critical to fill the gap between the findings from in vitro and the applications to human diseases, lack of effective and patient-like CCA animal models may contribute to limits of controlling progression of CCA. This review is focusing to provide the information about recently developed CCA animal models.

RECENT FINDINGS

Recent advancements in cell and molecular biology make it possible to mimic the pathogenicity of human CCA using various animal models. In this review, several up-to-date techniques and the examples to induce CCA in animal models (xenograft and orthotopic models, carcinogen-induced CCA model, genetically engineered mouse model for CCA) with resemblance of human CCA are discussed.

SUMMARY

Not only establishing animal models relevant to CCA is beneficial for its early diagnosis and therapy but also well suited experimental CCA models will guide the development of applicable treatment strategy for the hard-to-cure CCA.

Protective Effects of Guava Pulp on Cholestatic Liver Injury

Background. Cholestatic liver injury is a leading cause of chronic liver diseases involved with oxidative stress changes and inflammation; thus, antioxidant and anti-inflammation compound-rich guava may play a pivotal role in protecting against the cholestatic liver damages. Our aims for this study are to determine whether guava pulp (GP) has protective effects on cholestatic liver injury-induced mouse model and on interleukin-6 (IL-6) mediated proliferation of QBC939 cholangiocarcinoma cell line. Methods. Mice were induced to cholestatic liver damage by left and median bile duct ligation (LMBDL) surgery and then treated with GP. Plasma and liver samples were collected for biochemical and pathological assays. 5-Bromo-2'-deoxyuridine (BrdU) assay and Western blots were used to detect proliferation and gene expression in QBC939 cells, respectively. Results. Compared with LMBDL only group, in GP-treated mice, the levels of alanine aminotransferase (ALT) and bilirubin decreased, biliary epithelial cell proliferation and liver fibrogenesis were suppressed, Src/MEK/ERK1/2/c-Myc pathway and expressions of transforming growth factor β1(TGF-β1), tissue inhibitor of metalloproteinases TIMP), and procollagen 1α1(COL1α1) were downregulated significantly. Moreover, the GP extract reduced IL-6-enhanced QBC939 cell proliferation, p-ERK, and c-Myc expression as well. Conclusions. GP may provide a new perspective for the treatment of cholestatic liver injury.

A mouse model of cholestasis-associated cholangiocarcinoma and transcription factors involved in progression

BACKGROUND & AIMS

Cholestasis contributes to hepatocellular injury and promotes liver carcinogenesis. We created a mouse model of chronic cholestasis to study its effects on progression of cholangiocarcinoma and the oncogenes involved.

METHODS

To induce chronic cholestasis, Balb/c mice were given 2 weekly intraperitoneal injections of diethylnitrosamine (DEN); 2 weeks later, some mice also received left and median bile duct ligation (LMBDL) and, then 1 week later, were fed DEN, in corn oil, weekly by oral gavage (DLD). Liver samples were analyzed by immunohistochemical and biochemical assays; expression of Mnt and c-Myc was reduced by injection of small inhibitor RNAs.

RESULTS

Chronic cholestasis was induced by DLD and accelerated progression of cholangiocarcinoma, compared with mice given only DEN. Cystic hyperplasias, cystic atypical hyperplasias, cholangiomas, and cholangiocarcinoma developed in the DLD group at weeks 8, 12, 16, and 28, respectively. LMBDL repressed expression of microRNA (miR)-34a and let-7a, up-regulating Lin-28B, hypoxia-inducible factor (HIF)-1α, HIF-2α, and miR-210. Up-regulation of Lin-28B might inhibit let-7a, which is associated with development of cystic hyperplasias, cystic atypical hyperplasias, cholangiomas, and cholangiocarcinoma. Knockdown of c-Myc reduced progression of cholangiocarcinoma, whereas knockdown of Mnt accelerated its progression. Down-regulation of miR-34a expression might up-regulate c-Myc. The up-regulation of miR-210 via HIF-2α was involved in down-regulation of Mnt. Activation of the miR-34a-c-Myc and HIF-2α-miR-210-Mnt pathways caused c-Myc to bind the E-box element of cyclin D1, instead of Mnt, resulting in cyclin D1 up-regulation.

CONCLUSIONS

DLD induction of chronic cholestasis accelerated progression of cholangiocarcinoma, which is mediated by down-regulation of miR-34a, up-regulation miR-210, and replacement of Mnt by c-Myc in binding to cyclin D1.

c-Myc induction of programmed cell death may contribute to carcinogenesis: a perspective inspired by several concepts of chemical carcinogenesis

The c-Myc protein, encoded by c-myc gene, in its wild-type form can induce tumors with a high frequency and can induce massive programmed cell death (PCD) in most transgenic mouse models, with greater efficiency than other oncogenes. Evidence also indicates that c-Myc can cause proliferative inhibition, i.e. mitoinhibition. The c-Myc-induced PCD and mitoinhibition, which may be attributable to its inhibition of cyclin D1 and induction of p53, may impose a pressure of compensatory proliferation, i.e. regeneration, onto the initiated cells (cancer progenitor cells) that occur sporadically and are resistant to the mitoinhibition. The initiated cells can thus proliferate robustly and progress to a malignancy. This hypothetical thinking, i.e. the concurrent PCD and mitoinhibition induced by c-Myc can promote carcinogenesis, predicts that an optimal balance is achieved between cell death and ensuing regeneration during oncogenic transformation by c-Myc, which can better promote carcinogenesis. In this perspective, we summarize accumulating evidence and challenge the current model that oncoprotein induces carcinogenesis by promoting cellular proliferation and/or inhibiting PCD. Inspired by c-myc oncogene, we surmise that many tumor-suppressive or growth-inhibitory genes may also be able to promote carcinogenesis in a similar way, i.e. by inducing PCD and/or mitoinhibition of normal cells to create a need for compensatory proliferation that drives a robust replication of initiating cells.

The elements of human cyclin D1 promoter and regulation involved

Cyclin D1 is a cell cycle machine, a sensor of extracellular signals and plays an important role in G1-S phase progression. The human cyclin D1 promoter contains multiple transcription factor binding sites such as AP-1, NF-қB, E2F, Oct-1, and so on. The extracellular signals functions through the signal transduction pathways converging at the binding sites to active or inhibit the promoter activity and regulate the cell cycle progression. Different signal transduction pathways regulate the promoter at different time to get the correct cell cycle switch. Disorder regulation or special extracellular stimuli can result in cell cycle out of control through the promoter activity regulation. Epigenetic modifications such as DNA methylation and histone acetylation may involved in cyclin D1 transcriptional regulation.

Bile acids induce inflammatory genes in hepatocytes: a novel mechanism of inflammation during obstructive cholestasis

Inflammation contributes to liver injury during cholestasis. The mechanism by which cholestasis initiates an inflammatory response in the liver, however, is not known. Two hypotheses were investigated in the present studies. First, activation of Toll-like receptor 4 (TLR4), either by bacterial lipopolysaccharide or by damage-associated molecular pattern molecules released from dead hepatocytes, triggers an inflammatory response. Second, bile acids act as inflammagens, and directly activate signaling pathways in hepatocytes that stimulate production of proinflammatory mediators. Liver inflammation was not affected in lipopolysaccharide-resistant C3H/HeJ mice after bile duct ligation, indicating that Toll-like receptor 4 is not required for initiation of inflammation. Treatment of hepatocytes with bile acids did not directly cause cell toxicity but increased the expression of numerous proinflammatory mediators, including cytokines, chemokines, adhesion molecules, and other proteins that influence immune cell levels and function. Up-regulation of several of these genes in hepatocytes and in the liver after bile duct ligation required early growth response factor-1, but not farnesoid X receptor. In addition, early growth response factor-1 was up-regulated in the livers of patients with cholestasis and correlated with levels of inflammatory mediators. These data demonstrate that Toll-like receptor 4 is not required for the initiation of acute inflammation during cholestasis. In contrast, bile acids directly activate a signaling network in hepatocytes that promotes hepatic inflammation during cholestasis.

Induction of avian musculoaponeurotic fibrosarcoma proteins by toxic bile acid inhibits expression of glutathione synthetic enzymes and contributes to cholestatic liver injury in mice

We previously showed that hepatic expression of glutathione (GSH) synthetic enzymes and GSH levels fell 2 weeks after bile duct ligation (BDL) in mice. This correlated with a switch in nuclear anti-oxidant response element (ARE) binding activity from nuclear factor erythroid 2-related factor 2 (Nrf2) to c-avian musculoaponeurotic fibrosarcoma (c-Maf)/V-maf musculoaponeurotic fibrosarcoma oncogene homolog G (MafG). Our current aims were to examine whether the switch in ARE binding activity from Nrf2 to Mafs is responsible for decreased expression of GSH synthetic enzymes and the outcome of blocking this switch. Huh7 cells treated with lithocholic acid (LCA) exhibited a similar pattern of change in GSH synthetic enzyme expression as BDL mice. Nuclear protein levels of Nrf2 fell at 20 hours after LCA treatment, whereas c-Maf and MafG remained persistently induced. These changes translated to ARE nuclear binding activity. Knockdown of c-Maf or MafG individually blunted the LCA-induced decrease in Nrf2 ARE binding and increased ARE-dependent promoter activity, whereas combined knockdown was more effective. Knockdown of c-Maf or MafG individually increased the expression of GSH synthetic enzymes and raised GSH levels, and combined knockdown exerted an additive effect. Ursodeoxycholic acid (UDCA) or S-adenosylmethionine (SAMe) prevented the LCA-induced decrease in expression of GSH synthetic enzymes and promoter activity and prevented the increase in MafG and c-Maf levels. In vivo knockdown of the Maf genes protected against the decrease in GSH enzyme expression, GSH level, and liver injury after BDL.

CONCLUSION

Toxic bile acid induces a switch from Nrf2 to c-Maf/MafG ARE nuclear binding, which leads to decreased expression of GSH synthetic enzymes and GSH levels and contributes to liver injury during BDL. UDCA and SAMe treatment targets this switch.

p53 and the regulation of hepatocyte apoptosis: implications for disease pathogenesis

The interplay between p53 and apoptosis in diseases such as cancer, neurodegeneration, ischemia and atherosclerosis underscores the need to understand the complexity of p53 networks. Here, we highlight recent studies of p53-induced apoptosis in human diseases, with a focus on the modulation of liver cell apoptosis. In addition, recent work has provided new insights into mechanisms underlying the antiapoptotic functions of the endogenous bile acid ursodeoxycholic acid (UDCA), suggesting that the finely tuned, complex control of p53 by Mdm2 is a key step in the UDCA modulation of deregulated, p53-triggered apoptosis. The effect of targeting cell death signaling proteins has been established in preclinical models of human diseases. Finally, we review recent therapeutic strategies and clinical applications of targeted agents, with a particular emphasis on the potential use of UDCA.

Right hepatic lobectomy in elderly patients with hepatocellular carcinoma

BACKGROUND/AIMS

The outcome of hepatectomy in elderly patients with hepatocellular carcinoma have been reported, however neither the morphological nor functional hepatic regeneration in elderly patients have been fully investigated.

MATERIALS AND METHODS

Fifty-six patients with hepatocellular carcinoma, who underwent a right hepatic lobectomy over an 8-year period, were classified into three groups according to their age; group 1 (n = 7), more than 70 years of age; group 2 (n = 40), patients from 50 to 69 years of age and group 3 (n = 9), under 50 years of age. There were no significant differences regarding backgrounds or intra-operative parameters among the three groups. The perioperative hepatic function, postoperative complications and the regeneration rate of the remnant left lobe at 1 month after operation were compared.

RESULTS

No differences were found in the regeneration rate, however, the levels of the hepaplastin test and lecithin:cholesterol acyltransferase at 7 days after hepatectomy in group 1 (31.3%, 8.8 U) were significantly lower than those in groups 2 and 3 (37.4%, 18.4 U; 47.9%, 29.4 U, respectively). The incidence of hospital death due to hepatic failure in group 1 (42.9%) was also significantly higher than that of group 2 (5.0%) or group 3 (0%).

CONCLUSION

The decline of postoperative protein synthesis regardless of the voluminal regeneration is a characteristic of the elderly. This phenomenon might thus be an important promoter of postoperative hepatic failure which remains unpredictable using any type of examination. Therefore, at this time, a major hepatectomy is not recommended as a viable treatment alternative in the elderly.