Apoptosis as a mechanism for liver disease progression

Caspases compromise SLU7 and UPF1 stability and NMD activity during hepatocarcinogenesis

Background & Aims

The homeostasis of the cellular transcriptome depends on transcription and splicing mechanisms. Moreover, the fidelity of gene expression, essential to preserve cellular identity and function is secured by different quality control mechanisms including nonsense-mediated RNA decay (NMD). In this context, alternative splicing is coupled to NMD, and several alterations in these mechanisms leading to the accumulation of aberrant gene isoforms are known to be involved in human disease including cancer.

Methods

RNA sequencing, western blotting, qPCR and co-immunoprecipitation were performed in multiple silenced culture cell lines (replicates n ≥4), primary hepatocytes and samples of animal models (Jo2, APAP, Mdr2 -/- mice, n ≥3).

Results

Here we show that in animal models of liver injury and in human HCC (TCGA, non-tumoral = 50 vs. HCC = 374), the process of NMD is inhibited. Moreover, we demonstrate that the splicing factor SLU7 interacts with and preserves the levels of the NMD effector UPF1, and that SLU7 is required for correct NMD. Our previous findings demonstrated that SLU7 expression is reduced in the diseased liver, contributing to hepatocellular dedifferentiation and genome instability during disease progression. Here we build on this by providing evidence that caspases activated during liver damage are responsible for the cleavage and degradation of SLU7.

Conclusions

Here we identify the downregulation of UPF1 and the inhibition of NMD as a new molecular pathway contributing to the malignant reshaping of the liver transcriptome. Moreover, and importantly, we uncover caspase activation as the mechanism responsible for the downregulation of SLU7 expression during liver disease progression, which is a new link between apoptosis and hepatocarcinogenesis.

Impact and implications

The mechanisms involved in reshaping the hepatocellular transcriptome and thereby driving the progressive loss of cell identity and function in liver disease are not completely understood. In this context, we provide evidence on the impairment of a key mRNA surveillance mechanism known as nonsense-mediated mRNA decay (NMD). Mechanistically, we uncover a novel role for the splicing factor SLU7 in the regulation of NMD, including its ability to interact and preserve the levels of the key NMD factor UPF1. Moreover, we demonstrate that the activation of caspases during liver damage mediates SLU7 and UPF1 protein degradation and NMD inhibition. Our findings identify potential new markers of liver disease progression, and SLU7 as a novel therapeutic target to prevent the functional decay of the chronically injured organ.

Association of Circulating Markers of Microbial Translocation and Hepatic Inflammation with Liver Injury in Patients with Type 2 Diabetes

BACKGROUND

Virtually the entire spectrum of liver disease is observed in association with type 2 diabetes mellitus (T2DM); indeed, T2DM is now the most common cause of liver disease in the U.S. We conducted a pilot study to investigate the relevance of increased microbial translocation and systemic inflammation in the development of liver injury in patients with T2DM.

METHODS

Patients with T2DM (n = 17) and non-diabetic controls (NDC; n = 11) aged 25-80 yrs. participated in this study. Serum levels of endotoxin, calprotectin, soluble CD14 and CD163, and several inflammatory cytokines were measured. In addition to standard liver injury markers, ALT and AST, novel serum markers of liver injury, keratin 18 (K-18) M30 (apoptosis-associated caspase-cleaved keratin 18), and M65 (soluble keratin 18) were evaluated. Statistical analyses were performed using the Mann-Whitney test to assess differences between study groups. Pearson's correlation analysis was performed to determine the strength of association between two variables using GraphPad Prism 9.5.0 software.

RESULTS

Patients with T2DM had significantly higher levels of sCD14 in comparison to NDC, suggesting an increase in gut permeability, microbial translocation, and monocyte/macrophage activation. Importantly, relevant to the ensuing inflammatory responses, the increase in sCD14 in patients with T2DM was accompanied by a significant increase in sCD163, a marker of hepatic Kupffer cell activation and inflammation. Further, a positive correlation was observed between sCD163 and endotoxin and sCD14 in T2DM patients but not in NDC. In association with these changes, keratin 18 (K-18)-based serum markers (M65 and M30) that reflect hepatocyte death were significantly higher in the T2DM group indicating ongoing liver injury. Notably, both M65 and M30 levels correlated with sCD14 and sCD163, suggesting that immune cell activation and hepatic inflammation may be linked to the development of liver injury in T2DM.

CONCLUSIONS

These findings suggest that the pathogenic changes in the gut-liver axis, marked by increased microbial translocation, may be a major component in the etiology of hepatocyte inflammation and injury in patients with T2DM. However, larger longitudinal studies, including histological evidence, are needed to confirm these observations.

In vivo investigation of the anti-liver fibrosis impact of Balanites aegyptiaca/ chitosan nanoparticles

Balanites aegyptiaca (B. aegyptiaca) is an African herb with traditional medical applications. Various pathogenic factors cause hepatic fibrosis and require novel treatment alternatives. Nanoformulation-based natural products can overcome the available drug problems by increasing the efficacy of natural products targeting disease markers. The current study investigated B. aegyptiaca methanolic extract using high-pressure liquid chromatography (HPLC), and B. aegyptiaca/chitosan nanoparticles were prepared. In vivo, evaluation tests were performed to assess the curative effect of the successfully prepared B. aegyptiaca/chitosan nanoparticles. For 30 days, the rats were divided into six groups, typical and fibrosis groups, where the liver fibrosis groups received B. aegyptiaca extract, silymarin, chitosan nanoparticles, and B. aegyptiaca/chitosan nanoparticles daily. In the current investigation, phenolic molecules are the major compounds detected in B. aegyptiaca extract. UV showed that the prepared B. aegyptiaca /chitosan nanoparticles had a single peak at 280 nm, a particle size of 35.0 ± 6.0 nm, and a negative charge at - 8.3 mV. The animal studies showed that the synthetic B. aegyptiaca/chitosan nanoparticles showed substantial anti-fibrotic protective effects against CCl4-induced hepatic fibrosis in rats when compared with other groups through optimization of biochemical and oxidative markers, improved histological changes, and modulated the expression of Col1a1, Acta2 and Cxcl9 genes, which manage liver fibrosis. In conclusion, the current research indicated that the prepared B. aegyptiaca/chitosan nanoparticles improved histological structure and significantly enhanced the biochemical and genetic markers of liver fibrosis in an animal model.

Metformin exerts anti-liver fibrosis effect based on the regulation of gut microbiota homeostasis and multi-target synergy

Liver fibrosis can progress to cirrhosis if left untreated. Therefore, identifying effective antifibrotic drugs is crucial. This study aimed to investigate the role and potential mechanism of metformin in treating hepatic fibrosis based on the synergistic effect of multiple targets and the "intestine-liver axis" theory. A CCl4-induced liver fibrosis mouse model was established. We measured liver function, liver fibrosis indicators, oxidative stress and inflammation indices. Hematoxylin and eosin and Masson's trichrome staining were used to detect collagen deposition. The expression of apoptotic proteins, TGF-β/Smads and TIMP-1/MMPs was assessed. 16S rRNA and untargeted metabolomics (liquid chromatography-mass spectrometry) were used to assess mouse intestinal flora and metabolites, performing a comprehensive correlation analysis. Metformin improved the general status and liver function and decreased liver collagen deposition in CCl4-induced liver fibrotic mice. Compared with the control group, IL-6, TNF-α and COX-2 serum levels in the liver fibrosis group increased. Although not significantly different, the serum inflammatory marker levels in the metformin group were lower than those in the model group. Metformin decreased serum MDA and increased serum SOD activity, which increased and decreased, respectively, in the model group. Furthermore, metformin inhibited liver cell apoptosis, TGF-β1 expression and TIMP-1, while promoting Smad7 expression, MMP-1 and MMP-2 in fibrotic mice. 16S rRNA analysis indicated that metformin significantly ameliorated the Bacteroides, Helicobacter, Parabacteroides and Parasutterella imbalance. We identified 385 differential metabolites between the metformin and model groups. Prevotella abundance significantly decreased in the metformin group and positively correlated with decreased taurocholic acid levels. Metformin potentially reverses liver fibrosis by inhibiting inflammation, mitigating oxidative stress damage and suppressing hepatocyte apoptosis via intestinal flora metabolite regulation. Metformin also regulates the TGF-β/Smads and TIMP-1/MMPs signalling pathways. This study provides a theoretical basis for the clinical use of metformin in patients with liver fibrosis.

Efferocytosis in liver disease

The process of dead cell clearance by phagocytic cells, called efferocytosis, prevents inflammatory cell necrosis and promotes resolution and repair. Defective efferocytosis contributes to the progression of numerous diseases in which cell death is prominent, including liver disease. Many gaps remain in our understanding of how hepatic macrophages carry out efferocytosis and how this process goes awry in various types of liver diseases. Thus far, studies have suggested that, upon liver injury, liver-resident Kupffer cells and infiltrating monocyte-derived macrophages clear dead cells, limit inflammation, and, through macrophage reprogramming, repair liver damage. However, in unusual settings, efferocytosis can promote liver disease. In this review, we will focus on efferocytosis in various types of acute and chronic liver diseases, including metabolic dysfunction-associated steatohepatitis. Understanding the mechanisms and consequences of efferocytosis by hepatic macrophages has the potential to shed new light on liver disease pathophysiology and to guide new treatment strategies to prevent disease progression.

Chronic liver diseases: From development to novel pharmacological therapies: IUPHAR Review 37

Chronic liver diseases comprise a broad spectrum of burdensome diseases that still lack effective pharmacological therapies. Our research group focuses on fibrosis, which is a major precursor of liver cirrhosis. Fibrosis consists in a progressive disturbance of liver sinusoidal architecture characterised by connective tissue deposition as a reparative response to tissue injury. Multifactorial events and several types of cells participate in fibrosis initiation and progression, and the process still needs to be completely understood. The development of experimental models of liver fibrosis alongside the identification of critical factors progressing fibrosis to cirrhosis will facilitate the development of more effective therapeutic approaches for such condition. This review provides an overlook of the main process leading to hepatic fibrosis and therapeutic approaches that have emerged from a deep knowledge of the molecular regulation of fibrogenesis in the liver. LINKED ARTICLES: This article is part of a themed issue on Translational Advances in Fibrosis as a Therapeutic Target. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.22/issuetoc.

Transcription Factor Forkhead Box O1 Mediates Transforming Growth Factor-β1-Induced Apoptosis in Hepatocytes

Dysregulation of hepatocyte apoptosis is associated with several types of chronic liver diseases. Transforming growth factor-β1 (TGF-β1) is a well-known pro-apoptotic factor in the liver, which constitutes a receptor complex composed of TGF-β receptor I and II, along with transcription factor Smad proteins. As a member of the forkhead box O (Foxo) class of transcription factors, Foxo1 is a predominant regulator of hepatic glucose production and apoptosis. This study investigated the potential relationship between TGF-β1 signaling and Foxo1 in control of apoptosis in hepatocytes. TGF-β1 induced hepatocyte apoptosis in a Foxo1-dependent manner in hepatocytes isolated from both wild-type and liver-specific Foxo1 knockout mice. TGF-β1 activated protein kinase A through TGF-β receptor I-Smad3, followed by phosphorylation of Foxo1 at Ser273 in promotion of apoptosis in hepatocytes. Moreover, Smad3 overexpression in the liver of mice promoted the levels of phosphorylated Foxo1-S273, total Foxo1, and a Foxo1-target pro-apoptotic gene Bim, which eventually resulted in hepatocyte apoptosis. The study further demonstrated a crucial role of Foxo1-S273 phosphorylation in the pro-apoptotic effect of TGF-β1 by using hepatocytes isolated from Foxo1-S273A/A knock-in mice, in which the phosphorylation of Foxo1-S273 was disrupted. Taken together, this study established a novel role of TGF-β1→protein kinase A→Foxo1 signaling cascades in control of hepatocyte survival.

Enhanced apoptotic index in hepatocytes, Kupffer cells, and inflammatory infiltrate showed positive correlation with hepatic lesion intensity, parasite load, and clinical status in naturally Leishmania-infected dogs

It is unknown if Leishmania amastigote infections affect hepatocytes and Kupffer cell apoptosis, and the role played by apoptosis in liver lesions in leishmaniasis is still unclear. Clinically affected and subclinically infected dogs with leishmaniosis and uninfected controls were assessed. Parasite load, biochemical markers for evaluation of liver damage, morphometry (area, perimeter, number of inflammatory focus, major and minor diameters), apoptosis in hepatic tissue (hepatocytes, Kupffer cells, and inflammatory infiltrates) and cellularity in inflammatory foci were quantified. The parasite load in clinically affected dogs proved to be higher than in the other groups. All morphometric parameters (area, perimeter, number of inflammatory focus, major and minor diameters) from clinically affected were higher than the values found in the subclinically infected and uninfected control dogs. Only clinically affected dogs presented high levels of ALT, FA, GGT and cholesterol in serum. Strong positive correlation was observed between biochemical markers for evaluation of liver damage (ALT, FA, GGT and cholesterol) and hepatic apoptosis (hepatocytes, Kupffer cells, and inflammation). Clinically affected dogs showed a more intense hepatic lesion. Hepatocytes showed a higher rate of apoptosis in Leishmania-infected dogs than in uninfected control dogs. The Kupffer cell apoptotic index and apoptosis within the inflammatory infiltrates were higher in clinically affected dogs. The apoptotic index evaluated in hepatocytes, Kupffer cells, and inflammatory infiltrates showed a positive correlation with the intensity of the hepatic lesion, parasite load, and clinical status. Apoptotic cells also showed positive immunostaining for TUNEL, Bcl2, and Bax. Our data showed that hepatic apoptosis was related to the severity of liver damage, the progression of infection, and the parasite load in leishmaniasis. Apoptotic regulated cell recruitment modulated the inflammatory response and favored the survival and dissemination of parasites, depending on the clinical status of the Leishmania-infected dogs.

Anti-liver fibrosis activity of curcumin/chitosan-coated green silver nanoparticles

Liver fibrosis results from the hepatic accumulation of the extracellular matrix accompanied by a failure of the mechanisms responsible for matrix dissolution. Pathogenesis of liver fibrosis is associated with many proteins from different cell types. In the present study, in silico molecular docking analysis revealed that curcumin may inhibit the fibrosis-mediating proteins PDGF, PDGFRB, TIMP-1, and TLR-9 by direct binding. Nano-formulation can overcome curcumin problems, increasing the efficacy of curcumin as a drug by maximizing its solubility and bioavailability, enhancing its membrane permeability, and improving its pharmacokinetics, pharmacodynamics and biodistribution. Therefore, green silver nanoparticles (AgNPs) were synthesized in the presence of sunlight by means of the metabolite of Streptomyces malachiticus, and coated with curcumin-chitosan mixture to serve as a drug delivery tool for curcumin to target CCl₄-induced liver fibrosis mouse model. Fibrosis induction significantly increased hepatic gene expression of COL1A1, α-SMA, PDGFRB, and TIMP1, elevated hepatic enzymes, increased histopathological findings, and increased collagen deposition as determined by Mason's trichrome staining. Treatment with naked AgNPs tended to increase these inflammatory effects, while their coating with chitosan, similar to treatment with curcumin only, did not prevent the fibrogenic effect of CCl₄. The induction of liver fibrosis was reversed by concurrent treatment with curcumin/chitosan-coated AgNPs. In this nano form, curcumin was found to be efficient as anti-liver fibrosis drug, maintaining the hepatic architecture and function during fibrosis development. This efficacy can be attributed to its inhibitory role through a direct binding to fibrosis-mediating proteins such as PDGFRB, TIMP-1, TLR-9 and TGF-β.

Host and immunosuppression-related factors influencing fibrosis occurrence post liver transplantation

Post liver transplantation (LT) fibrosis has a negative impact on graft function. Cytokine production in the host immune response after LT may contribute to the variable CYP3A-dependent immunosuppressive drug disposition, with subsequent impact on liver fibrogenesis, together with host-related factors. We aimed to investigate whether the cytochrome P4503A5*3 (CYP3A5*3) or TBX21 genotypes impact post-LT liver fibrogenesis. Furthermore, the impact of immunosuppressants on cellular apoptosis has been evaluated using human hepatocytes harvested from cirrhotic explanted livers. We have enrolled 98 LT recipients that were followed for occurrence of liver fibrosis for at least 12 months. There was a statistically significant higher trough level of TAC in patients with homozygous CC-TBX21 genotype (7.83 ± 2.84 ng/ml) vs. 5.66 ± 2.16 ng/ml in patients without this genotype (p = 0.009). The following variables were identified as risk factors for fibrosis ≥2: donor age (p = 0.02), neutrophil to lymphocyte ratio (p = 0.04) and TBX21 genotype CC (p = 0.009). In the cell culture model cytometry analysis has indicated the lowest apoptotic cells percentage in human cirrhotic hepatocytes cultures treated with mycophenolate mofetil (MMF) (5%) and TAC + MMF (2%) whereas the highest apoptosis percentage was registered for the TAC alone (11%). The gene expression results are concordant to cytometry study results, indicating the lowest apoptotic effect for MMF and MMF + TAC immunosuppressive regimens. The allele 1993C of the SNP rs4794067 may predispose to the development of late significant fibrosis of the liver graft. MMF-based regimens have a favourable anti-apoptotic profile in vitro, supporting its use in case of LT recipients at high risk for liver graft fibrosis.

Phloridzin Reveals New Treatment Strategies for Liver Fibrosis

Liver fibrosis is an urgent public health problem which is difficult to resolve. However, various drugs for the treatment of liver fibrosis in clinical practice have their own problems during use. In this study, we used phloridzin to treat hepatic fibrosis in the CCl4-induced C57/BL6N mouse model, which was extracted from lychee core, a traditional Chinese medicine. The therapeutic effect was evaluated by biochemical index detections and ultrasound detection. Furthermore, in order to determine the mechanism of phloridzin in the treatment of liver fibrosis, we performed high-throughput sequencing of mRNA and lncRNA in different groups of liver tissues. The results showed that compared with the model group, the phloridzin-treated groups revealed a significant decrease in collagen deposition and decreased levels of serum alanine aminotransferase, aspartate aminotransferase, laminin, and hyaluronic acid. GO and KEGG pathway enrichment analysis of the differential mRNAs was performed and revealed that phloridzin mainly affects cell ferroptosis. Gene co-expression analysis showed that the target genes of lncRNA were obvious in cell components such as focal adhesions, intercellular adhesion, and cell–substrate junctions and in metabolic pathways such as carbon metabolism. These results showed that phloridizin can effectively treat liver fibrosis, and the mechanism may involve ferroptosis, carbon metabolism, and related changes in biomechanics.

Pathophysiological mechanisms of hepatic stellate cells activation in liver fibrosis

Liver fibrosis is a complex pathological process controlled by a variety of cells, mediators and signaling pathways. Hepatic stellate cells play a central role in the development of liver fibrosis. In chronic liver disease, hepatic stellate cells undergo dramatic phenotypic activation and acquire fibrogenic properties. This review focuses on the pathophysiological mechanisms of hepatic stellate cells activation in liver fibrosis. They enter the cell cycle under the influence of various triggers. The “Initiation” phase of hepatic stellate cells activation overlaps and continues with the “Perpetuation” phase, which is characterized by a pronounced inflammatory and fibrogenic reaction. This is followed by a resolution phase if the injury subsides. Knowledge of these pathophysiological mechanisms paved the way for drugs aimed at preventing the development and progression of liver fibrosis. In this respect, impairments in intracellular signaling, epigenetic changes and cellular stress response can be the targets of therapy where the goal is to deactivate hepatic stellate cells. Potential antifibrotic therapy may focus on inducing hepatic stellate cells to return to an inactive state through cellular aging, apoptosis, and/or clearance by immune cells, and serve as potential antifibrotic therapy. It is especially important to prevent the formation of liver cirrhosis since the only radical approach to its treatment is liver transplantation which can be performed in only a limited number of countries.

GBP5 promotes liver injury and inflammation by inducing hepatocyte apoptosis

Liver injury is the first step in causing fibrosis, cirrhosis, and liver cancer, leading to mortality. However, the drivers of progressive liver injury are still incompletely defined. Here, we identify GBP5 as a major factor causing liver injury and inflammation. We show that the expression of GBP5 is abnormally elevated in the damaged liver, and its expression depends at least partially on the NF-κB-inducing kinase (NIK)/NF-κB2 signaling pathway. Knockout of Gbp5 ameliorates D-galactosamine/lipopolysaccharide (GalN/LPS)-induced liver injury and inflammation. Conversely, liver-specific overexpression of GBP5 induces liver injury and inflammation. Mechanistically, GBP5 induces hepatocyte apoptosis through the activation of both calpain/caspase 12/caspase 3 and TNFα/caspase 8/caspase 3 signaling pathways. Inhibition of either calpain activity or caspase 3 prevents GBP5-induced cell death. Our data demonstrate that GBP5 expression is induced by toxins or the NIK signaling pathway, which promotes both extrinsic and intrinsic apoptosis signaling pathways and further induces liver injury, providing a novel drug target for the treatment of liver injury and inflammation.

A long way to go: caspase inhibitors in clinical use

Caspases are an evolutionary conserved family of cysteine-dependent proteases that are involved in many vital cellular processes including apoptosis, proliferation, differentiation and inflammatory response. Dysregulation of caspase-mediated apoptosis and inflammation has been linked to the pathogenesis of various diseases such as inflammatory diseases, neurological disorders, metabolic diseases, and cancer. Multiple caspase inhibitors have been designed and synthesized as a potential therapeutic tool for the treatment of cell death-related pathologies. However, only a few have progressed to clinical trials because of the consistent challenges faced amongst the different types of caspase inhibitors used for the treatment of the various pathologies, namely an inadequate efficacy, poor target specificity, or adverse side effects. Importantly, a large proportion of this failure lies in the lack of understanding various caspase functions. To overcome the current challenges, further studies on understanding caspase function in a disease model is a fundamental requirement to effectively develop their inhibitors as a treatment for the different pathologies. Therefore, the present review focuses on the descriptive properties and characteristics of caspase inhibitors known to date, and their therapeutic application in animal and clinical studies. In addition, a brief discussion on the achievements, and current challenges faced, are presented in support to providing more perspectives for further development of successful therapeutic caspase inhibitors for various diseases.

Multicenter, Double-Blind, Randomized Trial of Emricasan in Hepatitis C-Treated Liver Transplant Recipients With Residual Fibrosis or Cirrhosis

Despite achieving sustained virologic response (SVR) to hepatitis C virus (HCV) therapy, there remains a post liver transplantation population with advanced fibrosis/cirrhosis. Emricasan is an orally active, pan-caspase inhibitor that suppresses apoptosis and inflammation, potentially decreasing hepatic inflammation and fibrosis. We aimed to determine the safety and efficacy of emricasan (IDN-6556-07) in a double-blind, randomized, placebo-controlled, multicenter study in reducing or preventing the progression of hepatic fibrosis in HCV liver transplant recipients with residual fibrosis or cirrhosis after achieving SVR. A total of 64 participants were randomly assigned to receive 25 mg twice daily of emricasan or placebo in a 2:1 ratio for 24 months. 41 participants were randomly assigned to emricasan and 23 to placebo; 32 participants in the emricasan group (78.0%) and 19 who took a placebo (82.6%) completed the study. There was no difference in the primary endpoint (Ishak fibrosis stages F2-F5, improvement in fibrosis or stability; Ishak fibrosis stage F6, improvement) between the emricasan (77.1%) and placebo groups (74.1%); P = NS. There was no difference between the emricasan (54.5%) and placebo (60.7%) arms in the rate of fibrosis improvement alone. However, those in the prespecified F3 to F5 subgroup had higher rates of stability or improvement in fibrosis in the emricasan group (95.2%) compared with placebo (54.6%) (P = 0.01). The tolerability and safety profiles were similar in both groups. In conclusion, overall stability in the Ishak fibrosis stage was similar between emricasan and placebo groups at 24 months. However, there was improvement and/or stability in fibrosis stage in the prespecified F3 to F5 subgroup with emricasan versus placebo, suggesting that patients with moderate fibrosis may benefit with emricasan.

Formononetin protects against concanavalin-A-induced autoimmune hepatitis in mice through its anti-apoptotic and anti-inflammatory properties

Autoimmune hepatitis (AIH) is a chronic inflammatory liver disease that seriously threatens the health of humans globally. Formononetin (FMN) is a natural herb extract with multiple biological functions. In this study, an experimental model of AIH was established in mice through the use of concanavalin A (ConA). To investigate the effects of FMN on ConA-induced hepatitis, the mice were pretreated with 50 or 100 mg/kg body mass of FMN. The results show that FMN alleviated ConA-induced liver injury of mice in a dose-dependent manner. Moreover, pretreatment with FMN inhibited the apoptosis of hepatocytes in the ConA-treated mice through downregulating the expression of pro-apoptotic proteins (Bax, cleaved caspase 9, and cleaved caspase 3) and upregulating the expression of anti-apoptotic protein (Bcl-2). It was also found that the levels of proinflammatory cytokines were greatly reduced in the serum and liver tissues of mice pretreated with FMN. Further studies showed that FMN reduced the level of phosphorylated nuclear factor kappa B (p-NF-κB) p65 and enhanced the level of IκBα (inhibitor of NF-κB), suggesting that FMN inhibits the activation of the NF-κB signaling pathway. In addition, FMN inhibited activation of the NOD-like receptor protein 3 (NLRP3) inflammasome. Therefore, FMN could be a promising agent for the treatment of AIH.

Taxifolin, Extracted from Waste Larix olgensis Roots, Attenuates CCl4-Induced Liver Fibrosis by Regulating the PI3K/AKT/mTOR and TGF-β1/Smads Signaling Pathways

Purpose

Taxifolin is a kind of dihydroflavone and is usually used as a food additive and health food for its antioxidant, anti-inflammatory, and anti-tumor activities. The purpose of this research is to probe into the hepatoprotective activity and the molecular mechanism of taxifolin.

Materials and Methods

The liver fibrosis model was established by intraperitoneal injection of 5 mL/kg body weight of CCl₄ (20% CCl₄ peanut oil solution), and taxifolin was dissolved with 0.9% physiological saline and administered intragastrically to mice.

Results

The results indicated that CCl₄-induced significantly increased the serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in mice. Histopathological examination showed severe hepatocyte necrosis and hepatic tissue lesion. Immunohistochemical staining and rt-PCR analysis demonstrated that the expressions of inducible nitric oxide synthetase (iNOS), cyclooxygenase-2 (COX-2), IL-1β, IL-6, and TNF-α were increased. These changes were significantly reversed when treated with taxifolin. In addition, TUNEL staining and Bcl-2/Bax pathway confirmed that taxifolin significantly inhibited hepatocyte apoptosis. Besides, the research confirmed that taxifolin also inhibited the activation of hepatic stellate cells and the production of extracellular matrix (ECM) by regulating PI3K/AKT/mTOR and TGF-β1/Smads pathways.

Conclusion

Taxifolin inhibited inflammation, and attenuated CCl₄-induced oxidative stress and cell apoptosis by regulating PI3K/AKT/mTOR and TGF-β1/Smads pathways, which might in part contributed to taxifolin anti-hepatic fibrosis, further demonstrating that taxifolin may be an efficient hepatoprotective agent.

Endogenous production of n-3 polyunsaturated fatty acids protects mice from carbon tetrachloride-induced liver fibrosis by regulating mTOR and Bcl-2/Bax signalling pathways

NEW FINDINGS

What is the central question of this study? What is the protective benefit of n-3 polyunsaturated fatty acids (PUFAs) on liver fibrosis and what are the relevant signalling pathways in a transgenic mouse model overexpressing the mfat-1 enzyme? What is the main finding and its importance? n-3 PUFA elevation strongly prevented carbon tetrachloride (CCl₄ )-induced hepatic damage and inhibited the activation of hepatic stellate cells. n-3 PUFAs suppressed CCl₄ -induced activation of mTOR, elevated Bcl-2 expression, and reduced Bax level, suggesting that n-3 PUFAs can render strong protective effects against liver fibrosis and point to the potential of mfat-1 gene therapy as a treatment modality.

ABSTRACT

Liver fibrosis is a reversible wound healing response with excessive accumulation of extracellular matrix proteins. It is a globally prevalent disease with ultimately severe pathological consequences. However, very few current clinical therapeutic options are available. Nutritional addition of n-3 polyunsaturated fatty acids (PUFAs) can delay and lessen the development of liver fibrosis. Herein, this study examined the protective benefit of n-3 PUFAs on liver fibrosis and the relevant signalling pathways using a transgenic mouse model overexpressing the mfat-1 enzyme that converts n-6 to n-3 PUFAs. Male C57BL/6 wild-type and mfat-1 transgenic mice were administered carbon tetrachloride (CCl₄ ) or control corn oil by intraperitoneal injection. Blood alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were subsequently measured. CCl₄ -induced hepatic damage and fibrosis were assessed using haematoxylin-eosin and Masson's trichrome staining. Western blot assays were used to detect and quantify fibrosis-related proteins and mechanistic target of rapamycin (mTOR) and B-cell lymphoma 2 (Bcl-2)/Bcl-2-associated X protein (Bax) signalling components. The direct effect of docosahexaenoic acid (DHA) on primary hepatic stellate cells (HSCs) was also investigated in a co-culture experiment. n-3 PUFAs, as a result of mfat-1 activity, had a strong protective effect on liver fibrosis. The elevation of ALT and AST induced by CCl₄ was significantly lessened in the mfat-1 mice. Histological determination revealed the protective effects of n-3 PUFAs on liver inflammation and collagen deposition. Co-incubation with DHA reduced the expression of profibrogenic factors in the primary HSCs. Moreover, mfat-1 transgenic mice showed significant reduction of proteins that are involved in mTOR and Bcl-2/Bax signalling pathways. Collectively, these results suggest that n-3 PUFA elevation strongly prevents CCl₄ -induced hepatic damage by directly inhibiting the activation of HSCs and regulating the basal activity of the mTOR and Bcl-2/Bax signalling pathways. Gene therapy applying mfat-1 and elevating n-3 PUFAs represents a promising treatment strategy to prevent liver fibrosis.

Curcumin Can be Acts as Effective agent for Prevent or Treatment of Alcohol-induced Toxicity in Hepatocytes: An Illustrated Mechanistic Review

Previous studies have shown that alcohol abuse can cause serious liver damage and cirrhosis. The main pathway for these types of hepatocellular cell neurodegeneration is mitochondrial dysfunction, which causes lipid peroxidation and dysfunction of the glutathione ring and the defect of antioxidant enzymes in alcoholic hepatic cells. Alcohol can also initiate malicious inflammatory pathways and trigger the initiation and activation of intestinal and extrinsic apoptosis pathways in hepatocellular tissues that lead to cirrhosis. Previous studies have shown that curcumin may inhibit lipid peroxidation, glutathione dysfunction and restore antioxidant enzymes. Curcumin also modulates inflammation and the production of alcohol-induced biomarkers. Curcumin has been shown to play a critical role in the survival of alcoholic hepatocellular tissue. It has been shown that curcumin can induce and trigger mitochondrial biogenesis and, by this mechanism, prevent the occurrence of both intrinsic and extrinsic apoptosis pathways in liver cells that have been impaired by alcohol. According to this mechanism, curcumin may protect hepatocellular tissue from alcohol-induced cell degeneration and may therefore survive alcoholic hepatocellular tissue. . Based on these mechanisms, the protective functions of curcumin against alcohol-induced cell degeneration due to oxidative stress, inflammation, and apoptosis events in hepatocellular tissue have been recorded. Hence, in this research, we have attempted to evaluate and analyze the main contribution mechanism of curcumin cell defense properties against alcohol-induced hepatocellular damage, according to previous experimental and clinical studies, and in this way we report findings from major studies.

Multicenter Validation Study of a Diagnostic Algorithm to Detect NASH and Fibrosis in NAFLD Patients With Low NAFLD Fibrosis Score or Liver Stiffness

OBJECTIVES

Nonalcoholic steatohepatitis (NASH) and fibrosis play critical roles for the prognosis of patients with nonalcoholic fatty liver disease (NAFLD). Identification of patients at risk of NASH and fibrosis is therefore critical for disease management. NAFLD Fibrosis Score (NFS) and transient elastography (TE) have been suggested to exclude advanced fibrosis. However, there is increasing evidence that also patients with NASH and early fibrosis are at risk of disease progression and complications, emphasizing the need for improved noninvasive risk stratification in NAFLD.

METHODS

Because hepatocyte apoptosis plays an early role in NASH pathogenesis, we evaluated whether the apoptosis biomarker M30 might identify NAFLD patients who are at risk of NASH and fibrosis despite low NFS or TE values. Serum M30 levels were assessed by enzyme-linked immunosorbent assay in combination with NFS and/or TE in an exploration (n = 103) and validation (n = 100) cohort of patients with biopsy-proven NAFLD.

RESULTS

Most patients with low NFS (cutoff value < -1.455) revealed increased M30 levels (>200 U/L) in the exploration (62%) and validation (67%) cohort, and more than 70% of them had NASH, mostly with histological fibrosis. Vice versa, most patients with NFS < -1.455 but nonelevated M30 levels showed no NASH. NASH was also detected in most patients with indeterminate NFS (-1.455 to 0.676) but elevated M30 levels, from which ∼90% showed fibrosis. Similar results were obtained when using TE instead of NFS.

DISCUSSION

The combination of the M30 biomarker with NFS or TE enables a more reliable identification of patients with an increased risk of progressed NAFLD and improves patient stratification.

Acetaminophen-induced apoptosis: Facts versus fiction

An overdose of the widely used analgesic acetaminophen (APAP) is the most common cause of acute liver failure in the western world and hence is a clinically significant problem. Thus, mechanisms of APAP-induced hepatotoxicity have been the focus of extensive investigation for decades and it was established that APAP induces hepatocyte cell death by necrosis. Although APAP-induced necrosis shares some features of apoptosis induced by the intrinsic pathway, apoptotic cell death in this context was ruled out due to the absence of caspase activation and lack of protection by caspase inhibitors and missing morphological characteristics of apoptotic cells. Deeper mechanistic understanding of the cell death process after APAP in recent years has now revealed that cells die by programmed necrosis and apoptosis is not a relevant mode of cell death in this context. Hence, it is alarming to note that an increasing number of studies are being published purporting to indicate that APAP induces apoptotic cell death. These papers broadly measure "apoptotic markers" with questionable specificity such as Bax, Bcl-2 and caspase-3 protein expression, or use the terminal deoxynucleotidyl transferase dUTP nick end labeling assay as basis for the conclusion that there is apoptosis after APAP overdose. The misguided use of these apoptosis parameters in correlative studies without context or scientific rationale confuses the field and threatens to undo decades of careful mechanistic investigation into this topic. This review examines this emerging problem in detail and recommends approaches to correct it.

RELEVANCE FOR PATIENTS

Hepatotoxicity and acute liver failure caused by an acetaminophen overdose is a serious clinical problem in western countries. Understanding the mode of cell death and the signaling pathways involved is critical for developing new therapeutic approaches. Recent trends to claim that apoptosis is a relevant mode of cell death in acetaminophen hepatotoxicity are not justified by sound scientific data and will not lead to effective new drug development.

PI3K Catalytic Subunits α and β Modulate Cell Death and IL-6 Secretion Induced by Talc Particles in Human Lung Carcinoma Cells

Hydrated magnesium silicate (or "talc" particles) is a sclerosis agent commonly used in the management of malignant pleural effusions, a common symptom of metastatic diseases, including lung cancers. However, the direct effects of talc particles to lung carcinoma cells, which can be found in the malignant pleural effusion fluids from patients with lung cancer, are not fully understood. Here, we report a study of the signaling pathways that can modulate the cell death and IL-6 secretion induced by talc particles in human lung carcinoma cells. We found that talc-sensitive cells have higher mRNA and protein expression of PI3K catalytic subunits α and β. Further experiments confirmed that modulation (inhibition or activation) of the PI3K pathway reduces or enhances cellular sensitivity to talc particles, respectively, independent of the inflammasome. By knocking down specific PI3K isoforms, we also confirmed that both PI3Kα and -β mediate the observed talc effects. Our results suggest a novel role of the PI3K pathway in talc-induced cell death and IL-6 secretion in lung carcinoma cells. These cellular events are known to drive fibrosis, and thus further studies of the PI3K pathway may provide a better understanding of the mechanisms of talc sclerosis in the malignant pleural space.

Impact of osteopontin on the development of non-alcoholic liver disease and related hepatocellular carcinoma

BACKGROUND & AIMS

Osteopontin, a multifunctional protein and inflammatory cytokine, is overexpressed in adipose tissue and liver in obesity and contributes to the induction of adipose tissue inflammation and non-alcoholic fatty liver (NAFL). Studies performed in both mice and humans also point to a potential role for OPN in malignant transformation and tumour growth. To fully understand the role of OPN on the development of NAFL-derived hepatocellular carcinoma (HCC), we applied a non-alcoholic steatohepatitis (NASH)-HCC mouse model on osteopontin-deficient (Spp1^-/- ) mice analysing time points of NASH, fibrosis and HCC compared to wild-type mice.

METHODS

Two-day-old wild-type and Spp1^-/- mice received a low-dose streptozotocin injection in order to induce diabetes, and were fed a high-fat diet starting from week 4. Different cohorts of mice of both genotypes were sacrificed at 8, 12 and 19 weeks of age to evaluate the NASH, fibrosis and HCC phenotypes respectively.

RESULTS

Spp1^-/- animals showed enhanced hepatic lipid accumulation and aggravated NASH, as also increased hepatocellular apoptosis and accelerated fibrosis. The worse steatotic and fibrotic phenotypes observed in Spp1^-/- mice might be driven by enhanced hepatic fatty acid influx through CD36 overexpression and by a pathological accumulation of specific diacylglycerol species during NAFL. Lack of osteopontin lowered systemic inflammation, prevented HCC progression to less differentiated tumours and improved overall survival.

CONCLUSIONS

Lack of osteopontin dissociates NASH-fibrosis severity from overall survival and HCC malignant transformation in NAFLD, and is therefore a putative therapeutic target only for advanced chronic liver disease.

Studying the effects of sea cucumber ovum powder on nonalcoholic fatty liver disease by proteomics techniques in a rat model

Sea cucumber is a valuable marine food that has antioxidant, anti-diabetic, and anti-obesity functionalities. Sea cucumber ovum (SCO) may contain functional components, however, it is considered to be a waste product during industrial processing. In order to make good use of SCO, this work investigated the effects of freeze-dried SCO powder on NAFLD, using a rat model, through iBT labeling proteomics techniques, tracking changes in the hepatic protein profiles of rats whose diets were supplemented with SCO powder. Male rats were fed with standard food, a high fat diet (HFD), or a HFD supplemented with 150 mg per kg BW or 450 mg per kg BW SCO powder for 6 weeks. Compared with the HFD, low-dose SCO supplementation in the diet could significantly reduce body weight gain and liver weight. Furthermore, in total, 5922 proteins were identified, and 767 proteins were found to be significantly different proteins (p < 0.05) among all four groups. Most of the significantly different proteins were related to apoptosis and lipid metabolism. Fadd, Dci, and Aif1 have been identified as key proteins in the pathways related to apoptosis, lipid metabolism, and inflammation. The results in this study provide an overview of the SCO-induced changes in the liver proteome of NAFLD, which may help us to understand the molecular mechanism behind the effects of SCO on the alleviation of NAFLD.

Application of mesenchymal stem cell exosomes and their drug-loading systems in acute liver failure

Stem cell exosomes are nanoscale membrane vesicles released from stem cells of various origins that can regulate signal transduction pathways between liver cells, and their functions in intercellular communication have been recognized. Due to their natural substance transport properties and excellent biocompatibility, exosomes can also be used as drug carriers to release a variety of substances, which has great prospects in the treatment of critical and incurable diseases. Different types of stem cell exosomes have been used to study liver diseases. Due to current difficulties in the treatment of acute liver failure (ALF), this review will outline the potential of stem cell exosomes for ALF treatment. Specifically, we reviewed the pathogenesis of acute liver failure and the latest progress in the use of stem cell exosomes in the treatment of ALF, including the role of exosomes in inhibiting the ALF inflammatory response and regulating signal transduction pathways, the advantages of stem cell exosomes and their use as a drug‐loading system, and their pre‐clinical application in the treatment of ALF. Finally, the clinical research status of stem cell therapy for ALF and the current challenges of exosome clinical transformation are summarized.

Inevitable role of TGF-β1 in progression of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a major health concern and the most commonly diagnosed chronic liver manifestation among 25% worldwide population. Obesity, insulin resistance, accumulation of toxic lipid free radicals, generation of oxidative stress, overconsumption of fat containing dietary meals and lack of exercise are the paramount factors accountable for the development of NAFLD. During NAFLD, increased oxidative stress and production of enormous number of toxic free radicals activates a number of pro-inflammatory and inflammatory pathways. TGF-β signaling mechanisms play a central role in maintaining the normal homeostasis of liver. TGF-β1, one of the three isoforms of TGF-β family has significant role in different stages of chronic liver conditions. TGF-β1 promotes HSC activation and extracellular matrix production (ECM), which further contributes in the progression of NAFLD. In this review, we outline the role of TGF-β1 in different phases of progressive NAFLD along with the signaling mechanism.

Limonin ameliorates acetaminophen-induced hepatotoxicity by activating Nrf2 antioxidative pathway and inhibiting NF-κB inflammatory response via upregulating Sirt1

BACKGROUND

Limonin, a bioactive compound from citrus plants, exerts antioxidant activities, however its therapeutic potential in acetaminophen (APAP)-induced hepatotoxicity remains unclear.

PURPOSE

Our study aims to investigate the protective effect of limonin on APAP-induced hepatotoxicity and illuminate the underlying mechanisms.

STUDY

design In vitro, we chose L-02 cells to establish in vitro APAP-induced liver injury model. L-02 cells were treated with APAP (7.5 mM) for 24 h after pre-incubation with limonin (10, 25, 50 μM) or NAC (250 μM) for 2 h. In vivo, we used C57BL/6 mice as an in vivo APAP-induced liver injury model. C57BL/6 mice with pre-treatment of limonin (40, 80 mg/kg) or NAC (150 mg/kg) for 1 h, were given with a single dose of APAP (300 mg/kg).

METHODS

After pre-incubation with limonin (10, 25, 50 μM) for 2 h, L-02 cells were treated with APAP (7.5 mM) for 24 h.The experiments in vitro included MTT assay, Annexin V/PI staining, measurement of reactive oxygen species (ROS), quantitative real-time PCR analysis, Western blot analysis, immunofluorescence microscopy and analysis of LDH activity. Transfection of Nrf2 or Sirt1 siRNA was also conducted in vitro. In vivo, C57BL/6 mice with pre-treatment of limonin (40, 80 mg/kg) or NAC (150 mg/kg) for 1 h, were given with a single dose of APAP (300 mg/kg). Mice were sacrificed at 4, 12 h after APAP poisoning, and analysis of ALT and AST in serum, GSH level in liver tissues, liver histological observation and immunohistochemistry were performed.

RESULTS

Limonin increased the cell viability and alleviated APAP-induced apoptosis in hepatocytes. Limonin also inhibited APAP-induced mitochondrial-mediated apoptosis by decreasing the ratio of Bax/Bcl-2, recovery of mitochondrial membrane potential (MMP), inhibiting ROS production and cleavage of caspase-3 in L-02 cells. Moreover, limonin induced activation of Nrf2 and increased protein expression and mRNA levels of its downstream targets, including HO-1, NQO1 and GCLC/GCLM. The inhibition of limonin on apoptosis and promotion on Nrf2 antioxidative pathway were lessened after the application of Nrf2 siRNA. In addition, limonin inhibited NF-κB transcriptional activation, NF-κB-regulated genes and protein expression of inflammatory related proteins iNOS and COX2. Furthermore, limonin increased the protein expression of Sirt1. Sirt1 siRNA transfection confirmed that limonin activated Nrf2 antioxidative pathway and inhibited NF-κB inflammatory response by upregulating Sirt1. Finally, we established APAP-induced liver injury in vivo and demonstrated that limonin alleviated APAP-induced hepatotoxicity by activating Nrf2 antioxidative signals and inhibiting NF-κB inflammatory response via upregulating Sirt1.

CONCLUSION

In summary, this study documented that limonin mitigated APAP-induced hepatotoxicity by activating Nrf2 antioxidative pathway and inhibiting NF-κB inflammatory response via upregulating Sirt1, and demonstrated that limonin had therapeutic promise in APAP-induced liver injury.

Vitexin protects against ethanol-induced liver injury through Sirt1/p53 signaling pathway

In the present study, we aimed to investigate the therapeutic effect of Vitexin on inhibiting ethanol-induced liver damage and explore the underling mechanism. In vitro, the injury was induced in LO2 cell by 100 mM ethanol. Cell viability, AST, oxidative stress, inflammation, apoptosis rate, and related gene and protein expressions were assessed. Alcoholic liver injury model was made by intragastric infusion of alcohol for 4 weeks on male KM mice. Liver index, AST, ALT, TC, TG, TP, TBIL in serum and liver pathology were evaluated. Meanwhile, the level of SOD, MDA and TNF-α also were detected by Kits. Quantitative RT-PCR and Western blotting analysis the Sirt1/p53 pathway related gene and protein expressions. In vitro, Vitexin restored cytoactive and inhibited the releasing of AST induced by ethanol in LO2 cell. Vitexin treatment significantly suppressed the elevation of aminotransferase, blood lipid, UA in mice. Vitexin ameliorated liver pathological changes induced by ethanol. Vitexin supplement restored the decrease of Sirt1/Bcl-2 expression, restrained the elevation of caspase3, cleaved caspse-3, p53 and ac-p53 expression in vivo and in vitro. Vitexin has a protective effect against ethanol-induced liver damage, and the underlying mechanism is probably through Sirt1/p53 mediated mitochondrial apoptotic pathway.

LPS-induced inflammation desensitizes hepatocytes to Fas-induced apoptosis through Stat3 activation-The effect can be reversed by ruxolitinib

Recent studies have established a concept of tumour necrosis factor‐α (TNF‐α)/Fas signalling crosstalk, highlighting TNF‐α as a critical cytokine in sensitizing hepatocytes to death induced by Fas activation. However, in the exact inflammatory response, besides TNF‐α, many other mediators, that might modulate apoptotic response differentially, are released. To resolve the issue, we studied the effects of lipopolysaccharide (LPS), one of the crucial inductors of inflammation in the liver, on apoptotic outcome. We show that LPS‐induced inflammation diminishes the sensitivity of hepatocytes to Fas stimulus in vivo at caspase‐8 level. Analysis of molecular mechanisms revealed an increased expression of various pro‐inflammatory cytokines in non‐parenchymal liver cells and hepatocyte‐specific increase in Bcl‐xL, associated with signal transducer and activator of transcription 3 (Stat3) phosphorylation. Pre‐treatment with ruxolitinib, a selective Janus kinase (JAK) 1/2 inhibitor, prevented the LPS‐induced Stat3 phosphorylation and restored the sensitivity of hepatocytes to Fas‐mediated apoptosis. Furthermore, ruxolitinib pre‐treatment diminished the LPS‐induced Bcl‐xL up‐regulation without an inhibitory effect on LPS‐induced expression of pro‐inflammatory cytokines. In summary, although the reports are showing that the effects of isolated pro‐inflammatory mediators, such as TNF‐α or neutrophils, are pro‐apoptotic, the overall effect of inflammatory milieu on hepatocytes in vivo is Stat3‐dependent desensitization to Fas‐mediated apoptosis.

Protective role of melatonin in early-stage and end-stage liver cirrhosis

The liver is composed of hepatocytes, cholangiocytes, Kupffer cells, sinusoidal endothelial cells, hepatic stellate cells (HSCs) and dendritic cells; all these functional and interstitial cells contribute to the synthesis and secretion functions of liver tissue. However, various hepatotoxic factors including infection, chemicals, high‐fat diet consumption, surgical procedures and genetic mutations, as well as biliary tract diseases such as sclerosing cholangitis and bile duct ligation, ultimately progress into liver cirrhosis after activation of fibrogenesis. Melatonin (MT), a special hormone isolated from the pineal gland, participates in regulating multiple physiological functions including sleep promotion, circadian rhythms and neuroendocrine processes. Current evidence shows that MT protects against liver injury by inhibiting oxidation, inflammation, HSC proliferation and hepatocyte apoptosis, thereby inhibiting the progression of liver cirrhosis. In this review, we summarize the circadian rhythm of liver cirrhosis and its potential mechanisms as well as the therapeutic effects of MT on liver cirrhosis and earlier‐stage liver diseases including liver steatosis, nonalcoholic fatty liver disease and liver fibrosis. Given that MT is an antioxidative and anti‐inflammatory agent that is effective in eliminating liver injury, it is a potential agent with which to reverse liver cirrhosis in its early stage.

Biochemical and molecular-genetic indicators of inflammation and apoptosis in liver cirrhosis as an outcome of the progression of non-alcoholic steatohepatitis

AIM

A comparative analysis of the complex of clinical and laboratory indicators (including the content of cytokines in blood plasma and the level of expression of TNF and IL6 genes in peripheral leukocytes, as well as the level of biochemical and molecular-genetic indicators of apoptosis, such as the content of tissue polypeptide-specific antigen (TPS) in the blood, the activity of caspases 3, 8 and 9 and the expression level of the encoding genes in peripheral blood leukocytes) in patients with non-alcoholic fatty liver disease (NAFLD) with non-alcoholic steatohepatitis (NASH) of different activity, liver cirrhosis (LC) classes A and B and in the donors of control group.

MATERIALS AND METHODS

158 patients with NAFLD were examined: 116 patients with NASH diagnosed for the first time (NASH of weak, moderate and high activity) and 42 patients with the NAFLD at the stage of liver cirrhosis diagnosed for the first time (classes A and B according to the Child-Pugh classification). The control group consisted of 54 healthy donors. The clinical blood biochemistry, cytokine profile, tissue polypeptide-specific antigen content, the level of the TNF, IL6 gene and caspase gene transcription as well as caspase activity in peripheral blood leukocytes (PBL) were evaluated.

RESULTS

In the progression of NASH to LC, together with changes in general clinical parameters, the cytokine profile are changed due to an increase in the level of IL-6 and IL-1β; in peripheral leukocytes, the activity of caspase 9 increases and the activity of caspase 8 decreases compared to NASH, and the level of the TNF gene expression decreases as compared to NASH of high activity. These parameters can be considered as promising minimally invasive markers of progression of NAFLD to LC.

CONCLUSION

In nonalcoholic cirrhosis as an outcome of the progression of non-alcoholic steatohepatitis changes in clinical parameters (indicating the development of hepatocellular deficiency, violation of protein and lipid metabolism, progressive inflammation) are accompanied by specific changes in levels of biochemical and molecular-genetic indicators of apoptosis and inflammation. With the progression of NASH to LC, the cytokine profile changes due to an increase in the level of proinflammatory cytokines, the apoptosis processes triggered by the internal pathway increase and the activity of apoptosis activated via the external pathway decreases in PBL.

Ets-1 deficiency alleviates nonalcoholic steatohepatitis via weakening TGF-β1 signaling-mediated hepatocyte apoptosis

Hepatocyte apoptosis is a hallmark of nonalcoholic steatohepatitis (NASH) and contributes to liver injury, fibrosis, and inflammation. However, the molecular mechanisms underlying excessive hepatocyte apoptosis in NASH remain largely unknown. This study aimed to explore whether and how the v-ets avian erythroblastosis virus E26 oncogene homolog 1 (Ets-1) is involved in diet-induced hepatocyte apoptosis in mice. The study found that the expression level of hepatic Ets-1 was elevated in a NASH mouse model as a result of the activation of transforming growth factor beta1 (TGF-β1) signaling. In the presence of TGF-β1, phosphorylated mothers against decapentaplegic homolog 2/3 (p-Smad2/3) translocated to the binding sites of the Ets-1 promoter to upregulate the expression of Ets-1 in primary hepatocytes. In addition, Ets-1 bound directly to phosphorylated Smad3 (p-Smad3), thereby preventing the ubiquitination and proteasomal degradation of p-Smad3 and enhancing the activity of TGF-β1/Smad3 signaling. Consequently, elevated Ets-1 stimulated TGF-β1-induced hepatocyte apoptosis. However, Ets-1 knockdown alleviated diet-induced hepatocyte apoptosis and NASH with reduced liver injury, inflammation, and fibrosis. Taken together, Ets-1 had an adverse impact on hepatocyte survival under TGF-β1 treatment and accelerated the development of NASH in mice.

Salvianolic acid A attenuates CCl4-induced liver fibrosis by regulating the PI3K/AKT/mTOR, Bcl-2/Bax and caspase-3/cleaved caspase-3 signaling pathways

Background: Liver fibrosis occurs due to chronic liver disease due to multiple pathophysiological causes. The main causes for this condition are chronic alcohol abuse, nonalcoholic steatohepatitis, and infection due to hepatitis C virus. Currently, there is more and more information available about the molecular as well as cellular mechanisms, which play a role in the advancement of liver fibrosis. However, there is still no effective therapy against it.

Purpose: In order to find an effective treatment against liver fibrosis, our study explored whether salvianolic acid A (SA-A), a traditional Chinese medicine extracted from the plant Danshen, could effectively inhibit the liver fibrosis, which is induced by CCl₄ in vivo.

Methods: The effects of SA-A were evaluated by assessing the parameters related to liver fibrosis such as body weight, histological changes, and biochemical parameters. Thereafter, the related protein or gene levels of P13K/AKT/mTOR, Bcl-2/Bax and caspase-3/cleaved caspase-3 signaling pathways were determined by western blotting, real-time PCR or immunohistochemistry staining.

Results: According to the results of our study, SA-A could reduce liver fibrosis by inhibiting liver function, liver fibrosis index, collagen deposition, and improving the degree of liver fibrosis in rats. Mechanistically, the PI3K/AKT/mTOR signaling cascade was inhibited by SA-A to prevent the stimulation of hepatic stellate cell, as well as the synthesis of extracellular matrix, and regulated Bcl-2/Bax and caspase-3/cleaved caspase-3 signaling pathways to prevent hepatocyte apoptosis.

Conclusion: The novel findings of this study suggested that SA-A could reduce liver fibrosis and the molecular mechanisms behind it are closely associated with the regulation of PI3K/AKT/mTOR, Bcl-2/Bax and caspase-3/cleaved caspase-3 signaling pathways.

Modulations of Histone Deacetylase 2 Offer a Protective Effect through the Mitochondrial Apoptosis Pathway in Acute Liver Failure

The purpose of this study was to investigate the modulation of histone deacetylase 2 (HDAC2) on mitochondrial apoptosis in acute liver failure (ALF). The cellular model was established with LO2 cells stimulated by tumor necrosis factor alpha (TNF-α)/D-galactosamine (D-gal). Rats were administrated by lipopolysaccharide (LPS)/D-gal as animal model. The cell and animal models were then treated by HDAC2 inhibitor CAY10683. HDAC2 was regulated up or down by lentiviral vector transfection in LO2 cells. The mRNA levels of bcl2 and bax were detected by real-time PCR. The protein levels of HDAC2, bcl2, bax, cytochrome c (cyt c) in mitochondrion and cytosol, apoptosis protease activating factor 1 (apaf1), caspase 3, cleaved-caspase 3, caspase 9, cleaved-caspase 9, acetylated histone H3 (AH3), and histone H3 (H3) were assayed by western blot. Apoptosis was detected by flow cytometry. The serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), and total bilirubin (TBIL) levels were also assayed. The openness degree of the mitochondrial permeability transition pore (MPTP) was detected by ultraviolet spectrophotometry. The apoptosis of hepatocytes in liver tissues was determined by tunnel staining. The liver tissue pathology was detected by hematoxylin eosin (HE) staining. The ultrastructure of liver tissue was observed by electron microscopy. Compared with cell and rat model groups, the bax mRNA level was decreased, and bcl2 mRNA was increased in the CAY10683 treatment group. The protein levels of HDAC2, bax, cyt c in cytosol, apaf1, cleaved-caspase 3, and cleaved-caspase 9 were decreased, and the apoptosis rate was decreased (P < 0.05), whereas the protein level of bcl2 and cyt c in the mitochondrion was elevated (P < 0.05) in the CAY10683 treatment group. In the HDAC2 down- or upregulated LO2 cells, the mitochondrial apoptosis pathway was inhibited or activated, respectively. After being treated with TNF-α/D-gal in HDAC2 down- or upregulated LO2 cells, the mitochondrial apoptosis pathway was further suppressed or activated, respectively. The MPTP value was elevated in CAY10683-treated groups compared with the rat model group (P < 0.05). Liver tissue pathological damage and apoptotic index in the CAY10683-treated group were significantly reduced. In addition, AH3 was elevated in both cell and animal model groups (P < 0.05). Downregulated or overexpressed HDAC2 could accordingly increase or decrease the AH3 level, and TNF-α/D-gal could enhance the acetylation effect. These results suggested that modulations of histone deacetylase 2 offer a protective effect through the mitochondrial apoptosis pathway in acute liver failure.

Diallyl sulfide ameliorates carbon tetrachloride-induced hepatotoxicity in rats via suppressing stress-activated MAPK signaling pathways

The underlined effects of diallyl sulfide (DAS) against CCL₄ -induced oxidative, inflammatory, and apoptotic acute hepatic damage were assessed. Administration of DAS (50, 100, and 200 mg/kg) along with CCL ₄ effectively mitigated serum aspartate aminotransferase, alanine aminotransferase activities, MDA, TNF-α, IL-1β, and MCP-1 levels, as well as significantly restored HO-1, GSH levels and SOD activity in liver tissues compared with those in rats treated with CCL ₄ . Moreover, DAS inhibited CCL ₄ -induced increase of liver NF-κB (p65), Bax, p38 MAPK, and JNK protein expression. In addition, DAS accelerated protein expression of Nrf2 and Bcl-2. The hepatoprotective properties of DAS were further confirmed by the reduced severity of hepatic damage as demonstrated by histopathological findings. In conclusion, DAS achieved its protective potential against CCL4-induced hepatotoxicity through antiapoptotic activity, as well as the synchronized modulation of NF-κB and Nrf2 for the favor of antioxidant/anti-inflammatory effects via suppression of the upstream stress-activated MAPKs pathways.

Molecular pathways of nonalcoholic fatty liver disease development and progression

Nonalcoholic fatty liver disease (NAFLD) is a main hepatic manifestation of metabolic syndrome. It represents a wide spectrum of histopathological abnormalities ranging from simple steatosis to nonalcoholic steatohepatitis (NASH) with or without fibrosis and, eventually, cirrhosis and hepatocellular carcinoma. While hepatic simple steatosis seems to be a rather benign manifestation of hepatic triglyceride accumulation, the buildup of highly toxic free fatty acids associated with insulin resistance-induced massive free fatty acid mobilization from adipose tissue and the increased de novo hepatic fatty acid synthesis from glucose acts as the "first hit" for NAFLD development. NAFLD progression seems to involve the occurrence of "parallel, multiple-hit" injuries, such as oxidative stress-induced mitochondrial dysfunction, endoplasmic reticulum stress, endotoxin-induced, TLR4-dependent release of inflammatory cytokines, and iron overload, among many others. These deleterious factors are responsible for the triggering of a number of signaling cascades leading to inflammation, cell death, and fibrosis, the hallmarks of NASH. This review is aimed at integrating the overwhelming progress made in the characterization of the physiopathological mechanisms of NAFLD at a molecular level, to better understand the factor influencing the initiation and progression of the disease.

Anti-hepatofibrosis effect of Allium senescens in activated hepatic stellate cells and thioacetamide-induced fibrosis rat model

CONTEXT

Allium senescens Linn. (Liliaceae) (ASL) has been traditionally used in Korea and other Asian countries for improving digestive and liver functions.

OBJECTIVE

The anti-hepatofibrosis effect of ASL ethanol extract in cellular and experimental fibrosis rat model was investigated.

MATERIALS AND METHODS

In vitro cell viability, cell cycle and apoptosis in hepatic stellate cells (HSCs) were studied using MTT assay, flow cytometry and Annexin V-FITC/PI staining. Thioacetamide (TAA; 200 mg/kg, i.p.)-induced liver fibrosis model using Sprague Dawley rats (n = 10) was developed in vivo by injecting TAA twice per week for 13 weeks. ASL (25 and 100 mg/kg) and silymarin (50 mg/kg) were administered through oral gavage 2 times per week from 7th to 13th week. Specific fibrotic-related biomarkers such as aspartate transaminase (AST), alanine transaminase (ALT), glutathione and hydroxyproline levels in serum were analyzed by spectrophotometer using commercial kits. Morphological, histopathological and fibrotic-related gene expression such as TGF-β, Col1α1 and α-SMA in liver tissues was estimated by hematoxylin and eosin staining, Picrosirius red stain and quantitative real-time polymerase chain reaction, respectively.

RESULTS

ASL (0.1 mg/mL) and silymarin (0.05 mg/mL) treatment induced apoptosis (4.06% and 8.67%) in activated HSC-T6 cells, compared with control group (3.7%). The altered morphology in activated primary HSCs was also restored by ASL (0.1 mg/mL) treatment. Further, ASL (100 and 25 mg/kg) ameliorated the TAA-induced altered fibrotic-related biomarkers, histopathological changes and fibrotic-related gene expression significantly (p < 0.05 ∼ p < 0.001).

CONCLUSIONS

ASL can potentially be developed as a therapeutic agent in the treatment of hepatic fibrosis.

Silybin Alleviates Hepatic Steatosis and Fibrosis in NASH Mice by Inhibiting Oxidative Stress and Involvement with the Nf-κB Pathway

BACKGROUND AND AIM

Silybin is the major biologically active compound of silymarin, the standardized extract of the milk thistle (Silybum marianum). Increasing numbers of studies have shown that silybin can improve nonalcoholic steatohepatitis (NASH) in animal models and patients; however, the mechanisms underlying silybin's actions remain unclear.

METHODS

Male C57BL/6 mice were fed a methionine-choline deficient (MCD) diet for 8 weeks to induce the NASH model, and silybin was orally administered to the NASH mice. The effects of silybin on lipid accumulation, hepatic fibrosis, oxidative stress, inflammation-related gene expression and nuclear factor kappa B (NF-κB) activities were evaluated by biochemical analysis, immunohistochemistry, immunofluorescence, quantitative real-time PCR and western blot.

RESULTS

Silybin treatment significantly alleviated hepatic steatosis, fibrosis and inflammation in MCD-induced NASH mice. Moreover, silybin inhibited HSC activation and hepatic apoptosis and prevented the formation of MDBs in the NASH liver. Additionally, silybin partly reversed the abnormal expression of lipid metabolism-related genes in NASH. Further study showed that the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway played important roles in the silybin-derived antioxidant effect, as evidenced by the upregulation of Nrf2 target genes in the silybin treatment group. In addition, silybin significantly downregulated the expression of inflammation-related genes and suppressed the activity of NF-κB signaling.

CONCLUSIONS

Silybin was effective in preventing the MCD-induced increases in hepatic steatosis, fibrosis and inflammation. The effect was related to alteration of lipid metabolism-related gene expression, activation of the Nrf2 pathway and inhibition of the NF-κB signaling pathway in the NASH liver.

Molecular Mechanisms of Hepatocarcinogenesis Following Sustained Virological Response in Patients with Chronic Hepatitis C Virus Infection

Despite the success of direct-acting antiviral (DAA) agents in treating chronic hepatitis C virus (HCV) infection, the number of cases of HCV-related hepatocellular carcinoma (HCC) is expected to increase over the next five years. HCC develops over the span of decades and is closely associated with fibrosis stage. HCV both directly and indirectly establishes a pro-inflammatory environment favorable for viral replication. Repeated cycles of cell death and regeneration lead to genomic instability and loss of cell cycle control. DAA therapy offers >90% sustained virological response (SVR) rates with fewer side effects and restrictions than interferon. While elimination of HCV helps to restore liver function and reverse mild fibrosis, post-SVR patients remain at elevated risk of HCC. A series of studies reporting higher than expected rates of HCC development among DAA-treated patients ignited debate over whether use of DAAs elevates HCC risk compared to interferon. However, recent prospective and retrospective studies based on larger patient cohorts have found no significant difference in risk between DAA and interferon therapy once other factors are taken into account. Although many mechanisms and pathways involved in hepatocarcinogenesis have been elucidated, our understanding of drivers specific to post-SVR hepatocarcinogenesis is still limited, and lack of suitable in vivo and in vitro experimental systems has hampered efforts to examine etiology-specific mechanisms that might serve to answer this question more thoroughly. Further research is needed to identify risk factors and biomarkers for post-SVR HCC and to develop targeted therapies based on more complete understanding of the molecules and pathways implicated in hepatocarcinogenesis.

Magnesium Isoglycyrrhizinate Ameliorates Fibrosis and Disrupts TGF-β-Mediated SMAD Pathway in Activated Hepatic Stellate Cell Line LX2

Liver fibrosis is a histological change often attributed to the activation of hepatic stellate cells (HSCs) and the excessive formation of scar tissues in the liver. Advanced stages of the disease frequently lead to cirrhosis. Magnesium isoglycyrrhizinate (MgIG) has been accepted as a hepatoprotective drug with the potential of alleviating inflammatory conditions and thus promote liver recovery from viral- or drug-induced injury. While MgIG has been empirically integrated into the clinics to treat some liver diseases, its anti-fibrotic effect and the associated mechanisms remain poorly characterized. Herein, we demonstrated that 1 mg/ml MgIG attenuated the production of αSMA and collagen-1 in activated HSCs using TGF-β1-induced human HSCs LX2 as the fibrotic cell model. We found that MgIG exerts an inhibitory effect on the TGF-β-SMAD signaling pathway by arresting the binding of downstream transcription factors SMAD2/3 and SMAD4. Furthermore, MgIG was shown to suppress proliferation and induce senescence of activated LX2 cells. Protein expression of p27 and enzymatic activity of senescence-associated β-galactosidase were elevated upon exposure to MgIG. In addition, we observed that exposure of activated LX2 cells to MgIG reduces TGF-β-induced apoptosis. Interestingly, a lower toxicity profile was observed when human fetal hepatocytes LO2 were exposed to the same concentration and duration of the drug, suggesting the specificity of MgIG effect toward activated HSCs. Overall, hepatoprotective concentrations of MgIG is shown to exert a direct effect on liver fibrosis through inhibiting TGF-β-signaling, in which SMAD2/3 pathway could be one of the mechanisms responsible for the fibrotic response, thereby restoring the surviving cells toward a more quiescent phenotype. This provides critical mechanistic insights to support an otherwise empirical therapy.

Influence of Diabetes on Circulating Apoptotic Microparticles in Patients with Chronic Hepatitis C

BACKGROUND/AIM

Type 2 diabetes mellitus (DM) frequently occurs in patients with chronic hepatitis C (CHC) and is associated with atherosclerosis, in which circulating microparticles (MPs) play an important role. We asked whether the presence of DM affects endothelial-derived (EMPs) and platelet-derived microparticles (PMPs) levels; and whether MPs levels associate with biomarkers of inflammation and oxidative stress in patients with CHC.

MATERIALS AND METHODS

Overall, 136 patients were enrolled in the study, 86 CHC patients (41 with DM with moderate glycemic control), 20 outpatients with DM and 30 controls. Circulating MPs were phenotyped by flow cytometry.

RESULTS

When the MPs levels were analyzed individually in CHC patients, there was a positive association of plasma apoptotic MPs with oxidative stress markers. We report a hitherto undescribed relationship between diabetes prevalence and apoptotic MPs-associated inflammation in patients with CHC.

CONCLUSION

The presence of apoptotic MPs in the plasma of CHC patients, with increased levels being found in patients with DM and moderate glycemic control was herein demonstrated. The simultaneous monitoring of plasma apoptotic MPs, oxidative stress markers and inflammatory biomarkers can be helpful for the cardiovascular disease control in diabetic patients with CHC.

MicroRNAs in the pathogenesis and treatment of progressive liver injury in NAFLD and liver fibrosis

Non-alcoholic fatty liver disease (NAFLD) increases the risk of various liver injuries, ranging from simple steatosis to non-alcoholic steatohepatitis (NASH), fibrosis and cirrhosis, and ultimately hepatocellular carcinoma (HCC). Ample evidence has suggested that aberrant expression of microRNAs (miRNAs) is functionally involved in the activation of cellular stress, inflammation and fibrogenesis in hepatic cells, including hepatocytes, Kupffer and hepatic stellate cells (HSCs), at different pathological stages of NAFLD and liver fibrosis. Here, we overview recent findings on the potential role of miRNAs in the pathogenesis of NAFLD, including lipotoxicity, oxidative stress, metabolic inflammation and fibrogenesis. We critically assess the literatures on both human subjects and animal models of NAFLD and liver fibrosis with miRNA dysregulation and their mechanisms of actions in liver damage. We further highlight the potential use of miRNA mimics or antimiRNAs as therapeutic approaches for the prevention and treatment of NAFLD and liver fibrosis.