A Mechanistic Review of Cell Death in Alcohol-Induced Liver Injury

Cell Death in Liver Diseases: A Review

Regulated cell death (RCD) is pivotal in directing the severity and outcome of liver injury. Hepatocyte cell death is a critical event in the progression of liver disease due to resultant inflammation leading to fibrosis. Apoptosis, necrosis, necroptosis, autophagy, and recently, pyroptosis and ferroptosis, have all been investigated in the pathogenesis of various liver diseases. These cell death subroutines display distinct features, while sharing many similar characteristics with considerable overlap and crosstalk. Multiple types of cell death modes can likely coexist, and the death of different liver cell populations may contribute to liver injury in each type of disease. This review addresses the known signaling cascades in each cell death pathway and its implications in liver disease. In this review, we describe the common findings in each disease model, as well as the controversies and the limitations of current data with a particular focus on cell death-related research in humans and in rodent models of alcoholic liver disease, non-alcoholic fatty liver disease and steatohepatitis (NASH/NAFLD), acetaminophen (APAP)-induced hepatotoxicity, autoimmune hepatitis, cholestatic liver disease, and viral hepatitis.

Gentiopicroside prevents alcoholic liver damage by improving mitochondrial dysfunction in the rat model

Gentianae Radix et Rhizoma is a medical plant that is widely cultivated in China, North Korea, Japan, and Russia, and gentiopicroside is one of its major active compounds. In this study, the hepatoprotective activity of gentiopicroside on rats with alcoholic liver damage (ALD) was evaluated using the transaminase and blood lipid levels and antioxidant capacity. The potential mechanism of hepatoprotective effect of gentiopicroside was evaluated by mitochondrial function detection, gas chromatography-mass spectrometry (GC-MS) metabolomic analysis, and anti-apoptosis analysis. Results showed that the gentiopicroside exhibited good hepatoprotective activity on rats with ALD by decreasing the transaminase levels, regulating the blood lipid levels, and increasing the antioxidant capacity. The potential mechanisms were related to regulating mitochondrial dysfunction by recovering mitochondrial membrane potential level, adenosine triphosphate concentration, activities of key enzymes in tricarboxylic acid cycle, and activities of complex I-V, regulating micromolecular metabolism and anti-apoptosis. These findings supported the further exploration of Gentianae Radix et Rhizoma as effective phytotherapy to prevent and treat ALD.

Physcion Protects Against Ethanol-Induced Liver Injury by Reprogramming of Circadian Clock

The circadian clock plays a key role in our daily physiology and metabolism. Alcohol consumption disrupts the circadian rhythm of metabolic genes in the liver; however, the potential contribution of circadian clock modulation to alcoholic liver disease (ALD) is unknown. We identified a novel liver protective agent, physcion, which can alleviate fat accumulation and inflammation in ALD mice via reprogramming the hepatic circadian clock. The model of alcoholic hepatitis was established by intragastrically administering ethanol. In vitro, physcion was investigated by treating HepG2 cells with ethanol. The role of circadian clock in Physcion caused liver protection was tested by knocking down the core circadian gene Bmal1. Physcion application caused reduced lipogenesis and alleviated inflammation in alcohol-induced mice. In alcoholic hepatosteatosis models, physcion upregulated the core circadian genes. And the circadian misalignment triggered by ethanol was efficiently reversed by physcion. Physcion attenuated lipogenesis via reprogramming the circadian clock in HepG2 cells. Suppression of Bmal1 by RNA interference abolished the protective of physcion. In addition, Physcion binds to the active pocket of BMAL1 and promotes its expression. The study identified the novel liver protective effects of physcion on alcohol-induced liver injury, and modulation of the core circadian clock regulators contributes to ALD alleviation. More importantly, strategies targeting the circadian machinery, for example, Bmal1, may prove to be beneficial treatment options for this condition.

NLRP12 negatively regulates EtOH-induced liver macrophage activation via NF-κB pathway and mediates hepatocyte apoptosis in alcoholic liver injury

Alcohol-induced liver injury is characterized by abnormal liver dysfunction and excessive inflammation response. Recent years a wealth of data have been yielded indicating that EtOH (ethyl alcohol)-induced macrophage activation along with liver inflammation plays a dominating role in the progression of alcohol-induced liver injury. Here we found high expression of NLRP12 (Nucleotide-binding oligomerization domain protein 12, which is generally considered to be a negative regulator of inflammatory response) in EtOH-fed mouse liver tissue, primary Kupffer cells and EtOH-induced RAW264.7 cells. Additionally, overexpression of NLRP12 following Ad (adenovirus)-NLRP12-EGFP contributed to the attenuation of steatosis and inflammation in EtOH-fed mice model and EtOH-primed RAW264.7 cells. In parallel, Knockdown of NLRP12 aggravated the inflammatory response in RAW264.7 cells triggered by EtOH. Meanwhile, after administration of overexpression or inhibition of NLRP12 expression in vitro, the expression of phosphorylated protein of NF-kB signaling pathway was significantly affected. After increasing or decreasing the expression of NLRP12 in RAW264.7 cells, AML-12 cells were cultured with the supernatant of RAW264.7 cells stimulated by EtOH, and the percent of apoptosis ratio of AML-12 cells was remarkably altered. The study suggested that reduced inflammatory response induced by NLRP12-mediated inhibition of NF-kB pathway participated in the decrease of hepatocyte apoptosis in alcohol-induced liver injury. Collectively, these findings suggested the significance of NLRP12-mediated macrophage activation in alcohol-induced liver injury.

Cell Death and Liver Disease

Cell death is now reclassified into several types based on the mechanisms and morphologic phenotype. Understanding of such classifications offers insights into the pathogenesis of liver disease, as well as diagnostic or therapeutic implications. Apoptosis is recognized relatively easily due to its unique morphology, but lytic cell death may occur in the form of accidental necrosis, mitochondria permeability transition-driven necrosis, necroptosis, pyroptosis, ferroptosis, and parthanatos. The cell may be engulfed by neighboring cells due to a loss of integrin signaling or cancer cell competition by entosis, a type of cell death. The classification also includes mechanistically termed cell death such as autophagy-dependent cell death and lysosome-dependent cell death. These different types of cell death may occur uniquely in certain liver diseases but may coexist in the evolution of the disease. They occur in parenchymal and non-parenchymal liver cells, as well as inflammatory cells, causing distinct pathologic consequences. This review briefly covers the recently revised classifications of cell death and discusses their relevance to liver diseases of different etiologies.

Dendrobium officinale Flower Extraction Mitigates Alcohol-Induced Liver Injury in Mice: Role of Antisteatosis, Antioxidative, and Anti-Inflammatory

The study aimed to evaluate the protective effect of Dendrobium officinale flower extraction (DOFE) on alcohol-induced liver injury and its probable mechanisms in mice. The chemical composition of DOFE was performed via UPLC/MS. Male Kunming mice were used to establish alcohol-induced liver injury models by oral gavage of 56% alcohol. Results showed that DOFE dramatically attenuated the increased serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), total cholesterol (TC), and triacylglycerol (TG). Meanwhile, hematoxylin and eosin and Oil Red O staining showed that DOFE attenuated degeneration, inflammatory infiltration, and lipid droplet accumulation. DOFE was also found to suppress the activity of malonaldehyde (MDA) and enhanced the level of glutathione (GSH) and the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) in the liver. The protection of DOFE against oxidative stress was associated with the downregulation of hepatic cytochrome P450 2E1 (CYP2E1) and upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and NAD(P)H quinone oxidoreductase l (NQO1). Additionally, DOFE suppressed inflammation via downregulating Toll-like receptor-4 (TLR-4) and nuclear factor kappa-B P65 (NF-κB P65). Thus, DOFE exhibited a significant protective effect against alcohol-induced liver injury through its antisteatosis, antioxidative, and anti-inflammatory effect.

Dipeptide YA is Responsible for the Positive Effect of Oyster Hydrolysates on Alcohol Metabolism in Single Ethanol Binge Rodent Models

Accumulative alcohol hangovers cause liver damage through oxidative and inflammatory stress. Numerous antioxidant and anti-inflammatory reagents have been developed to reduce alcohol hangovers, but these reagents are still insignificant and have limitations in that they can cause liver toxicity. Oyster hydrolysate (OH), another reagent that has antioxidant and anti-inflammatory activity, is a product extracted through an enzymatic hydrolysis process from oysters (Crassostrea gigas), which can be easily eaten in meals. This study was aimed at determining the effects of OH on alcohol metabolism, using a single high dose of ethanol (EtOH) administered to rodents, by monitoring alcohol metabolic enzymes, oxidative stress signals, and inflammatory mediators. The effect of tyrosine-alanine (YA) peptide, a main component of OH, on EtOH metabolism was also identified. In vitro experiments showed that OH pretreatment inhibited EtOH-induced cell death, oxidative stress, and inflammation in liver cells and macrophages. In vivo experiments showed that OH and YA pre-administration increased alcohol dehydrogenase, aldehyde dehydrogenase, and catalase activity in EtOH binge treatment. In addition, OH pre-administration alleviated CYP2E1 activity, ROS production, apoptotic signals, and inflammatory mediators in liver tissues. These results showed that OH and YA enhanced EtOH metabolism and had a protective effect against acute alcohol liver damage. Our findings offer new insights into a single high dose of EtOH drinking and suggest that OH and YA could be used as potential marine functional foods to prevent acute alcohol-induced liver damage.

Obesity and binge alcohol intake are deadly combination to induce steatohepatitis: A model of high-fat diet and binge ethanol intake

Obesity and binge drinking often coexist and work synergistically to promote steatohepatitis; however, the underlying mechanisms remain obscure. In this mini-review, we briefly summarize clinical evidence of the synergistical effect of obesity and heavy drinking on steatohepatitis and discuss the underlying mechanisms obtained from the study of several mouse models. High-fat diet (HFD) feeding and binge ethanol synergistically induced steatohepatitis and fibrosis in mice with significant intrahepatic neutrophil infiltration; such HFD-plus-ethanol treatment markedly up-regulated the hepatic expression of many chemokines with the highest fold (approximately 30-fold) induction of chemokine (C-X-C motif) ligand 1 (Cxcl1), which contributes to hepatic neutrophil infiltration and liver injury. Furthermore, HFD feeding activated peroxisome proliferator-activated receptor gamma that subsequently inhibited CXCL1 upregulation in hepatocytes, thereby forming a negative feedback loop to prevent neutrophil overaction; whereas binge ethanol blocked this loop and then exacerbated CXCL1 elevation, neutrophil infiltration, and liver injury. Interestingly, inflamed mouse hepatocytes attracted neutrophils less effectively than inflamed human hepatocytes due to the lower induction of CXCL1 and the lack of the interleukin (IL)-8 gene in the mouse genome, which may be one of the reasons for difficulty in development of mouse models of alcoholic steatohepatitis and nonalcoholic steatohepatitis (NASH). Hepatic overexpression of Cxcl1 and/or IL-8 promoted steatosis-to-NASH progression in HFD-fed mice by inducing neutrophil infiltration, oxidative stress, hepatocyte death, fibrosis, and p38 mitogen-activated protein kinase activation. Collectively, obesity and binge drinking synergistically promote steatohepatitis via the induction of CXCL1 and subsequent hepatic neutrophil infiltration.

Non-alcoholic Fatty Liver Disease and Alcohol-Related Liver Disease: Two Intertwined Entities

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease worldwide, with a prevalence of 25-30%. Since its first description in 1980, NAFLD has been conceived as a different entity from alcohol-related fatty liver disease (ALD), despite that, both diseases have an overlap in the pathophysiology, share genetic-epigenetic factors, and frequently coexist. Both entities are characterized by a broad spectrum of histological features ranging from isolated steatosis to steatohepatitis and cirrhosis. Distinction between NAFLD and ALD is based on the amount of consumed alcohol, which has been arbitrarily established. In this context, a proposal of positive criteria for NAFLD diagnosis not considering exclusion of alcohol consumption as a prerequisite criterion for diagnosis had emerged, recognizing the possibility of a dual etiology of fatty liver in some individuals. The impact of moderate alcohol use on the severity of NAFLD is ill-defined. Some studies suggest protective effects in moderate doses, but current evidence shows that there is no safe threshold for alcohol consumption for NAFLD. In fact, given the synergistic effect between alcohol consumption, obesity, and metabolic dysfunction, it is likely that alcohol use serves as a significant risk factor for the progression of liver disease in NAFLD and metabolic syndrome. This also affects the incidence of hepatocellular carcinoma. In this review, we summarize the overlapping pathophysiology of NAFLD and ALD, the current data on alcohol consumption in patients with NAFLD, and the effects of metabolic dysfunction and overweight in ALD.

Alpha-lipoic acid protects against pressure overload-induced heart failure via ALDH2-dependent Nrf1-FUNDC1 signaling

Alpha-lipoic acid (α-LA), a well-known antioxidant, was proved to active ALDH2 in nitrate tolerance and diabetic animal model. However, the therapeutic advantage of α-LA for heart failure and related signaling pathway have not been explored. This study was designed to examine the role of α-LA–ALDH2 in heart failure injury and mitochondrial damage. ALDH2 knockout (ALDH2^−/−) mice and primary neonatal rat cardiomyocytes (NRCMs) were subjected to assessment of myocardial function and mitochondrial autophagy. Our data demonstrated α-LA significantly reduced the degree of TAC-induced LV hypertrophy and dysfunction in wild-type mice, not in ALDH2^−/− mice. In molecular level, α-LA significantly restored ALDH2 activity and expression as well as increased the expression of a novel mitophagy receptor protein FUNDC1 in wild-type TAC mice. Besides, we confirmed that ALDH2 which was activated by α-LA governed the activation of Nrf1–FUNDC1 cascade. Our data suggest that α-LA played a positive role in protecting the heart against adverse effects of chronic pressure overload.

Role of Mesencephalic Astrocyte-Derived Neurotrophic Factor in Alcohol-Induced Liver Injury

Consumption of alcohol in immoderate quantity induces endoplasmic reticulum (ER) stress response (alcohol-induced ER stress). Mesencephalic astrocyte-derived neurotrophic factor (MANF), an ER stress-inducible protein, works as an evolutionarily conserved regulator of systemic and liver metabolic homeostasis. In this study, the effects of MANF on alcohol-induced liver injury were explored by using hepatocyte-specific MANF-knockout mice (MANF ^ΔHep) in a chronic-plus-binge alcohol feeding model. We found that alcohol feeding upregulated MANF expression and MANF ^ΔHep mice exhibited more severe liver injury with extra activated ER stress after alcohol feeding. In addition, we found that MANF deficiency activated iNOS and p65 and increased the production of NO and anti-inflammatory cytokines, which was further enhanced after alcohol treatment. Meanwhile, MANF deletion upregulated the levels of CYP2E1, 4-HNE, and MDA and downregulated the levels of GSH and SOD. These results indicate that MANF has potential protection on alcohol-induced liver injury, and the underlying mechanisms may be associated with meliorating the overactivated ER stress triggered by inflammation and oxidative stress via inhibiting and reducing NO/NF-κB and CYP2E1/ROS, respectively. Therefore, MANF might be a negative regulator in alcohol-induced ER stress and participate in the crosstalk between the NF-κB pathway and oxidative stress in the liver. Conclusions. This study identifies a specific role of MANF in alcohol-induced liver injury, which may provide a new approach for the treatment of ALI.

Therapeutic potential of genipin in various acute liver injury, fulminant hepatitis, NAFLD and other non-cancer liver diseases: More friend than foe

Genipin is an aglycone derived from the geniposide, the most abundant iridoid glucoside constituent of Gardenia jasminoides Ellis. For decades, genipin is the focus of studies as a versatile compound in the treatment of various pathogenic conditions. In particularly, Gardenia jasminoides Ellis has long been used in traditional Chinese medicine for the prevention and treatment of liver disease. Mounting experimental data has proved genipin possesses therapeutic potential for cholestatic, septic, ischemia/reperfusion-triggered acute liver injury, fulminant hepatitis and NAFLD. This critical review is a reflection on the valuable lessons from decades of research regarding pharmacological activities of genipin. Of note, genipin represents choleretic effect by potentiating bilirubin disposal and enhancement of genes in charge of the efflux of a number of organic anions. The anti-inflammatory capability of genipin is mediated by suppression of the production and function of pro-inflammatory cytokines and inflammasome. Moreover, genipin modulates various transcription factor and signal transduction pathway. Genipin appears to trigger the upregulation of several key genes encoding antioxidant and xenobiotic-metabolizing enzymes. Furthermore, the medicinal impact of genipin extends to modulation of regulated cell death, including autophagic cell death, apoptosis, necroptosis and pyroptosis, and modulation of quality of cellular organelle. Another crucial effect of genipin appears to be linked to dual role in targeting uncoupling protein 2 (UCP2). As a typical UCP2-inhibiting compound, genipin could inhibit AMP-activated protein kinase or NF-κB in circumstance. On the contrary, reactive oxygen species production and cellular lipid deposits mediated by genipin through the upregulation of UCP2 is observed in liver steatosis, suggesting the precise role of genipin is disease-specific. Collectively, we comprehensively summarize the mechanisms and pathways associated with the hepatoprotective activity of genipin and discuss potential toxic impact. Notably, our focus is the direct medicinal effect of genipin itself, whereas its utility as a crosslinking agent in tissue engineering is out of scope for the current review. Further studies are therefore required to disentangle these complicated pharmacological properties to confer this natural agent a far greater potency.

Paeoniflorin, a Natural Product With Multiple Targets in Liver Diseases-A Mini Review

Paeoniflorin is derived from Paeonia suffruticosa Andr., Paeonia lactiflora Pall., or Paeonia veitchii Lynch and has been used in traditional medical applications for more than 2,000 years. Paeoniflorin is a monoterpenoid glycoside with various effects on liver diseases. Recent studies have revealed that paeoniflorin demonstrates a wide range of activities, including hepatic protection, cholestasis alleviation, liver fibrosis attenuation, nonalcoholic fatty liver disease prevention, and hepatocellular carcinoma inhibition involved in multiple pathways. Moreover, anti-inflammation, antioxidation, and immune regulation with the regulation of TLR4-NF-κB, ROCK/NF-κB, HO-1, mitochondria-dependent as well as HMGB1‐TLR4 signaling pathways are correlated with hepatic protection in liver injury and nonalcoholic fatty liver disease. Antioxidative mechanisms, anti-inflammation, and hepatic transporter regulation involved in NOX4, PI3K/Akt/Nrf2, NF‐κB, NTCP, BSEP, as well as MRP2 signals are mainly relevant to the anticholestatic effect of paeoniflorin. The inhibition of hepatic stellate cell activation and alleviation of extracellular matrix deposition via vast signals such as mTOR/HIF-1α, TGF-β1/Smads, and JAK2/STAT6 are primarily involved in the antifibrotic effect of paeoniflorin. The regulation of macrophages also contributes to the alleviation effect on liver fibrosis. In addition, the reduction of invasion, metastasis, and adhesion and the induction of apoptosis-related targets, including Bax, Bcl-2, and caspase-3, are related to its effect on hepatocellular carcinoma. The literature indicates that paeoniflorin might have potent efficacy in complex liver diseases and demonstrates the profound medicinal value of paeoniflorin.

Hepatoprotective effects of melatonin and celecoxib against ethanol-induced hepatotoxicity in rats

Objectives: Several studies demonstrated the antioxidant and anti-inflammatory role of melatonin and celecoxib. This study is designed to explore the underlying mechanism of hepatoprotective effects of melatonin and celecoxib against ethanol-induced hepatotoxicity by morphological, and biochemical approaches.Materials and methods: Adult male rats were divided into five groups: saline, ethanol, melatonin, and celecoxib were administered for 11 consecutive days after ethanol injection. Biochemical analyses were performed for the determination of glutathione (GSH), glutathione S-transferase (GST), and inducible nitric oxide (iNOS). Immunohistochemistry was performed to determine the level of different inflammatory markers.Results: Histopathological results showed that ethanol-induced marked hepatic injury leads to cloudy swelling, hydropic degeneration, apoptosis, and focal necrosis in all hepatic zones. Biochemical analysis revealed significant increases in serum transaminases and alkaline phosphatase in the ethanol group. Oxidative stress associated with attenuated antioxidant enzymes was also spotted in the ethanol group, as ethanol down-regulated GSH, GST, and upregulated NO. Additionally, ethanol increased the activation and the expression of tumor necrotic factor (TNF-α), p-NF_KB, and COX2. Finally, hepatic cellular apoptosis was clearly obvious in ethanol intoxicated animals using activated JNK staining.Conclusion: These results provided pieces of evidence that the hepatoprotective effect of melatonin and celecoxib is possibly mediated through the modulation of JNK and TNF-α signaling pathways with subsequent suppression of inflammatory and apoptotic processes.

Noninvasive 40-Hz Light Flicker Rescues Circadian Behavior and Abnormal Lipid Metabolism Induced by Acute Ethanol Exposure via Improving SIRT1 and the Circadian Clock in the Liver-Brain Axis

Sirtuin 1 (SIRT1) is a protein deacetylase with important cellular functions, as it regulates numerous processes, including the circadian rhythm in peripheral tissues. Efforts are ongoing to reveal how Sirt1 can be used to treat diseases, such as alcoholic liver disease (ALD), Alzheimer's disease, and liver fibrosis. We have recently shown that noninvasive exposure to 40-Hz light flicker activates hypothalamic SIRT1 gene expression, thereby regulating the central circadian clock. This study investigated the effects of 40-Hz light flicker in a mouse model of ALD. RNA sequencing (RNA-seq) analysis was performed to explore the potential pathways affected by 40-Hz light flicker. We found that 40-Hz light flicker significantly decreased the acute ethanol-induced increases in serum alanine aminotransferase (ALT) and serum triglyceride (TG) levels and reduced fat-droplet accumulation in mouse livers. Additionally, 40-Hz light flicker significantly suppressed ethanol-induced increases in sterol regulatory element binding protein 1 (SREBP-1) and fatty acid synthase (Fasn) levels. Furthermore, the ethanol induced significant decreases in both Sirt1 levels and phosphorylation of adenosine monophosphate-activated protein kinase subunit (AMPKα), compared with those in the control group. Strikingly, pretreatment with 40-Hz light flicker ameliorated such ethanol-induced decreases in SIRT1 levels and AMPKα phosphorylation. In addition, ethanol-induced increases in levels of brain and muscle arnt-like protein-1 (BMAL1), circadian locomotor output cycles kaput (CLOCK), and period 2 (PER2) were reversed by 40-Hz light flicker. RNA-seq analysis revealed significant differences in expression of genes related to the AMPK signalling. Moreover, ethanol consumption altered mRNA levels of Sirt1 and circadian genes in the suprachiasmatic nucleus (SCN), indicating that ethanol influenced central pacemaker genes; however, 40-Hz light flicker reversed these ethanol-induced changes. Taken together, our findings demonstrate that 40-Hz light flicker rapidly influence the SCN and exhibits inhibitory properties on hepatic lipogenesis, indicating that 40-Hz light flicker has therapeutic potential for preventing alcoholic liver steatosis.

The Candida albicans exotoxin candidalysin promotes alcohol-associated liver disease

BACKGROUND & AIMS

Alcohol-associated liver disease is a leading indication for liver transplantation and a leading cause of mortality. Alterations to the gut microbiota contribute to the pathogenesis of alcohol-associated liver disease. Patients with alcohol-associated liver disease have increased proportions of Candida spp. in the fecal mycobiome, yet little is known about the effect of intestinal Candida on the disease. Herein, we evaluated the contributions of Candida albicans and its exotoxin candidalysin in alcohol-associated liver disease.

METHODS

C. albicans and the extent of cell elongation 1 (ECE1) were analyzed in fecal samples from controls, patients with alcohol use disorder and those with alcoholic hepatitis. Mice colonized with different and genetically manipulated C. albicans strains were subjected to the chronic-plus-binge ethanol diet model. Primary hepatocytes were isolated and incubated with candidalysin.

RESULTS

The percentages of individuals carrying ECE1 were 0%, 4.76% and 30.77% in non-alcoholic controls, patients with alcohol use disorder and patients with alcoholic hepatitis, respectively. Candidalysin exacerbates ethanol-induced liver disease and is associated with increased mortality in mice. Candidalysin enhances ethanol-induced liver disease independently of the β-glucan receptor C-type lectin domain family 7 member A (CLEC7A) on bone marrow-derived cells, and candidalysin does not alter gut barrier function. Candidalysin can damage primary hepatocytes in a dose-dependent manner in vitro and is associated with liver disease severity and mortality in patients with alcoholic hepatitis.

CONCLUSIONS

Candidalysin is associated with the progression of ethanol-induced liver disease in preclinical models and worse clinical outcomes in patients with alcoholic hepatitis.

LAY SUMMARY

Candidalysin is a peptide toxin secreted by the commensal gut fungus Candida albicans. Candidalysin enhances alcohol-associated liver disease independently of the β-glucan receptor CLEC7A on bone marrow-derived cells in mice without affecting intestinal permeability. Candidalysin is cytotoxic to primary hepatocytes, indicating a direct role of candidalysin on ethanol-induced liver disease. Candidalysin might be an effective target for therapy in patients with alcohol-associated liver disease.

Phenotypic high-throughput screening platform identifies novel chemotypes for necroptosis inhibition

Regulated necrosis or necroptosis, mediated by receptor-interacting kinase 1 (RIPK1), RIPK3 and pseudokinase mixed lineage kinase domain-like protein (MLKL), contributes to the pathogenesis of inflammatory, infectious and degenerative diseases. Recently identified necroptosis inhibitors display moderate specificity, suboptimal pharmacokinetics, off-target effects and toxicity, preventing these molecules from reaching the clinic. Here, we developed a cell-based high-throughput screening (HTS) cascade for the identification of small-molecule inhibitors of necroptosis. From the initial library of over 250,000 compounds, the primary screening phase identified 356 compounds that strongly inhibited TNF-α-induced necroptosis, but not apoptosis, in human and murine cell systems, with EC50 < 6.7 μM. From these, 251 compounds were tested for RIPK1 and/or RIPK3 kinase inhibitory activity; some were active and several have novel mechanisms of action. Based on specific chemical descriptors, 110 compounds proceeded into the secondary screening cascade, which then identified seven compounds with maximum ability to reduce MLKL activation, IC50 >100 μM, EC50 2.5-11.5 μM under long-term necroptosis execution in murine fibroblast L929 cells, and full protection from ATP depletion and membrane leakage in human and murine cells. As a proof of concept, compound SN-6109, with binding mode to RIPK1 similar to that of necrostatin-1, confirmed RIPK1 inhibitory activity and appropriate pharmacokinetic properties. SN-6109 was further tested in mice, showing efficacy against TNF-α-induced systemic inflammatory response syndrome. In conclusion, a phenotypic-driven HTS cascade promptly identified robust necroptosis inhibitors with in vivo activity, currently undergoing further medicinal chemistry optimization. Notably, the novel hits highlight the opportunity to identify new molecular mechanisms of action in necroptosis.

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.

A novel acidic polysaccharide from the residue of Panax notoginseng and its hepatoprotective effect on alcoholic liver damage in mice

This study presented the first purification and characterization of a hepatoprotective polysaccharide (PNPS-0.5 M) from the residue of Panax notoginseng (Burk.) F.H. Chen. This polysaccharide included a backbone of (4 → 1)-linked GalA and branches of (1→)-linked Araf, (1→)-linked Rhap, and (5 → 1)-linked Araf and had an extremely high molecular weight (2600 kDa). We investigated the hepatoprotective effects of PNPS-0.5 M on mice with alcoholic liver damage (ALD). After administration of PNPS-0.5 M, the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), triglyceride (TG), and hepatic malondialdehyde (MDA) were reduced to normal. In contrast, hepatic levels of alcohol dehydrogenase (ADH) and the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were elevated to normal. Further investigations indicated that PNPS-0.5 M activated Nrf2 signaling as a protective mechanism against Cyp2e1 toxicity in ALD mice. Meanwhile, it strengthened the ADH pathway and suppressed the CAT pathway of alcohol metabolism to prevent peroxide accumulation, thereby ameliorating ALD. In the present study, we describe a novel acidic polysaccharide from P. notoginseng with hepatoprotective activity that facilitates the development and utilization of P. notoginseng resources.

Activation of ALDH2 attenuates high glucose induced rat cardiomyocyte fibrosis and necroptosis

Necroptosis is one of a regulated programmed death mode, fibrosis is closely related with cell death. It has been reported that inhibition of necroptosis can play the protective role in cardiac ischemia and reperfusion injury, stroke and other diseases, but the mechanisms of aldehyde dehydrogenases 2 (ALDH2) against high glucose induced neonatal rat ventricular primary cardiomyocytes fibrosis and necroptosis had not been elucidated clearly. This study was to observe the effect of ALDH2 on high glucose (HG) induced myocardial fibrosis and necroptosis in primary rat cardiomyocytes model. In contrast to normal glucose group, in HG group, with the decreases of ALDH2 activity, mRNA and protein levels, the cardiomyocytes viability was decreased, reactive oxygen species (ROS), the inflammation factors - tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β) levels, collagen I (col I) and col III mRNA expressions and tissue inhibitors of matrix metalloproteinase 4 (TIMP4) protein expression were increased, while matrix metalloproteinase 14 (MMP14) protein level, the ratio of MMP14/TIMP4 were decreased, and the necroptosis key factors - the receptor interacting protein 1 (RIP1), RIP3 and mixed lineage kinase domain-like protein (MLKL) at mRNA and protein expressions were increased, the inflammasome core proteins - NLRP3 and ASC protein expressions were also increased, the apoptosis rate and necrosis rate were also increased. When the cardiomyocytes were treated with Alda-1 (the ALDH2 agonist) in HG intervention, the cell viability, ALDH2 activity, mRNA and protein levels, MMP14 protein level, the ratio of MMP14/TIMP4 were higher, ROS and TNF-α, IL-6, IL-1β levels, RIP1, RIP3, MLKL, NLRP3 and ASC expressions, col I and col III, TIMP4 expressions, the apoptosis rate and necrosis rate were lower than in HG group. Daidzin, the antagonist of ALDH2 abolished the role of Alda-1. In summary, ALDH2 maybe is a key regulator in high glucose induced cardiomyocytes injury. Activation of ALDH2 prevented the happening of fibrosis, apoptosis and necroptosis in high glucose induced primary cardiomyocytes injury model, the protective effects were related to the inhibiting of oxidative stress and inflammation, changing of MMP14 and TIMP4, then inhibiting the happening of fibrosis, apoptosis and necroptosis. These findings advance our understanding of the intensive mechanisms of ALDH2's cardioprotection, and provide the targeted basis for clinical diabetes treatment.

Pathogenesis, Early Diagnosis, and Therapeutic Management of Alcoholic Liver Disease

Alcoholic liver disease (ALD) refers to the damages to the liver and its functions due to alcohol overconsumption. It consists of fatty liver/steatosis, alcoholic hepatitis, steatohepatitis, chronic hepatitis with liver fibrosis or cirrhosis, and hepatocellular carcinoma. However, the mechanisms behind the pathogenesis of alcoholic liver disease are extremely complicated due to the involvement of immune cells, adipose tissues, and genetic diversity. Clinically, the diagnosis of ALD is not yet well developed. Therefore, the number of patients in advanced stages has increased due to the failure of proper early detection and treatment. At present, abstinence and nutritional therapy remain the conventional therapeutic interventions for ALD. Moreover, the therapies which target the TNF receptor superfamily, hormones, antioxidant signals, and MicroRNAs are used as treatments for ALD. In particular, mesenchymal stem cells (MSCs) are gaining attention as a potential therapeutic target of ALD. Therefore, in this review, we have summarized the current understandings of the pathogenesis and diagnosis of ALD. Moreover, we also discuss the various existing treatment strategies while focusing on promising therapeutic approaches for ALD.

Ameliorative effects of autophagy inducer, simvastatin on alcohol-induced liver disease in a rat model

Alcoholic liver disease (ALD) encompasses a variety of liver injuries with various underlying mechanisms but still no effective treatment. So we aimed to monitor the influence of simvastatin on alcohol-induced liver injury and elucidate the underlying mechanisms of its cytoprotective effect. Thirty male albino rats were randomly divided into five equal groups. Group 1 (control): received a standard diet; group 2: received simvastatin (10 mg kg^-1  day ^-1 ) once a day orally for 8 weeks; group 3: received 20% ethanol (7.9 g kg ^-1  day ^-1 ) daily orally for 8 weeks; group 4: received 20% ethanol along with same simvastatin dose daily for 8 weeks; group 5: received 20% ethanol orally for 8 weeks then received the same simvastatin dose for the next 8 weeks. Serum alanine aminotransferase, aspartate aminotransferase, total cholesterol, triglycerides, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol were measured. Liver tissue malondialdehyde, reduced glutathione levels, and superoxide dismutase activity were estimated. B-cell lymphoma 2 and C/EBP homologous protein levels were evaluated by enzyme linked immunosorbent assay (ELISA). Light chain 3-II and peroxisome proliferation-activated receptor gamma messenger RNA expression was assessed by real-time polymerase chain reaction. Immunohistochemical staining was performed using anti-rat tumor necrosis factor-alpha antibody. Our results revealed that simvastatin treatment was able to ameliorate alcohol-induced liver damage; the improved biochemical data were confirmed by histopathological evaluation. Simvastatin being an autophagy inducer was able to prevent and reverse alcohol-induced liver changes via induction of autophagy, attenuation of oxidative stress, inflammation, and endoplasmic reticulum stress-induced apoptosis. Therefore, our findings suggest that treatment with simvastatin may be a useful approach in the management strategy of ALD.

Modulation of autophagy in human diseases strategies to foster strengths and circumvent weaknesses

Autophagy is central to the maintenance of intracellular homeostasis across species. Accordingly, autophagy disorders are linked to a variety of diseases from the embryonic stage until death, and the role of autophagy as a therapeutic target has been widely recognized. However, autophagy-associated therapy for human diseases is still in its infancy and is supported by limited evidence. In this review, we summarize the landscape of autophagy-associated diseases and current autophagy modulators. Furthermore, we investigate the existing autophagy-associated clinical trials, analyze the obstacles that limit their progress, offer tactics that may allow barriers to be overcome along the way and then discuss the therapeutic potential of autophagy modulators in clinical applications.

Inflammatory pathways in alcoholic steatohepatitis

Inflammatory processes are primary contributors to the development and progression of alcoholic steatohepatitis (ASH), with severe alcoholic hepatitis characterised by non-resolving inflammation. Inflammation in the progression of ASH is a complex response to microbial dysbiosis, loss of barrier integrity in the intestine, hepatocellular stress and death, as well as inter-organ crosstalk. Herein, we review the roles of multiple cell types that are involved in inflammation in ASH, including resident macrophages and infiltrating monocytes, as well as other cell types in the innate and adaptive immune system. In response to chronic, heavy alcohol exposure, hepatocytes themselves also contribute to the inflammatory process; hepatocytes express a large number of chemokines and inflammatory mediators and can also release damage-associated molecular patterns during injury and death. These cellular responses are mediated and accompanied by changes in the expression of pro- and anti-inflammatory cytokines and chemokines, as well as by signals which orchestrate the recruitment of immune cells and activation of the inflammatory process. Additional mechanisms for cell-cell and inter-organ communication in ASH are also reviewed, including the roles of extracellular vesicles and microRNAs, as well as inter-organ crosstalk. We highlight the concept that inflammation also plays an important role in promoting liver repair and controlling bacterial infection. Understanding the complex regulatory processes that are disrupted during the progression of ASH will likely lead to better targeted strategies for therapeutic interventions.

Urinary acrolein metabolite levels in severe acute alcoholic hepatitis patients

Alcohol-associated liver disease (ALD) remains a major health concern worldwide. Alcohol consumption gives rise to reactive/toxic acrolein, a pathogenic mediator of liver injury in experimental ALD. Elevated acrolein adducts and metabolites are detectable in blood and urine. This study evaluates the major urinary acrolein metabolite, 3-hydroxypropylmercapturic acid (HPMA), in patients with acute alcoholic hepatitis (AAH) and examines its association with disease severity and markers of hepatic inflammation and injury. Urine HPMA was significantly higher in patients with severe [model for end-stage liver disease (MELD) ≥ 20] AAH compared with nonsevere AAH (MELD ≤ 19) or non-alcohol-consuming controls, suggesting that urine HPMA is a novel noninvasive biomarker in severe AAH. The association between HPMA and MELD in patients with AAH was nonlinear. In patients with nonsevere AAH, there was a positive trend, although not significant, whereas in severe AAH the association was negative, indicative of extensive injury and glutathione depletion. Consistent with the multifactorial etiology of ALD, our data identified strong combined effects of HPMA and proinflammatory cytokines on hepatocyte cell death, thereby supporting the pathogenic role of acrolein in liver injury. HPMA, together with IL-1β, showed robust associations with cytokeratin 18 caspase-cleaved fragment (CK18-M30; adjusted R² = 0.812, P = 0.016) and cytokeratin 18 full-length protein (CK18-M65; adjusted R² = 0.670, P = 0.048); similarly, HPMA, with IL-8, correlated with CK18-M30 (adjusted R² = 0.875, P = 0.007) and CK18-M65 (adjusted R² = 0.831, P = 0.013). The apoptosis index (CK18-M30:CK18-M65 ratio) strongly correlated with HPMA, together with IL-1β (adjusted R² = 0.777, P = 0.022) or tumor necrosis factor-α (TNFα; adjusted R² = 0.677, P = 0.046). In patients with severe AAH, IL-1β, IL-8, and TNFα are the predominant proinflammatory cytokines that interact with HPMA and play important mediating roles in influencing the extent/pattern of liver cell death. NEW & NOTEWORTHY This is the first study to examine the urinary acrolein metabolite 3-hydroxypropylmercapturic acid (HPMA) in alcoholic liver disease. HPMA was higher in patients with severe acute alcoholic hepatitis (AAH) compared with controls or nonsevere AAH and may be a novel selective, noninvasive biomarker for severe AAH. Consistent with the multifactorial etiology of alcohol-associated liver disease, we identified strong combined effects of HPMA and proinflammatory cytokines (IL-1β, IL-8, and TNFα) on the extent/pattern of liver cell death, thereby supporting the pathogenic role of acrolein.

Dysregulation of Sqstm1, mitophagy, and apoptotic genes in chronic exposure to arsenic and high-fat diet (HFD)

Arsenic (As) is a toxic and hazardous metalloid. Unfortunately, its presence in drinking water together with wrong nutritional patterns is associated with an increase in the occurrence of metabolic disorders in young people. Degradation of mitochondria is presented by a specific form of autophagy called mitophagy which is an important landmark leading to apoptosis during lipotoxicity. Lipotoxicity and cellular toxicity due to arsenic intake can lead to changes in mitophagy and apoptosis. The protein derived from SQSTM1 gene, also called p62, plays an important role in energy homeostasis in the liver, and it can contribute to the regulation of autophagic responses given its effect on signaling of mTOR, MAPK, and NF-KB. Consequently, changes in Sqstm1, mitophagy (BNIP3), and apoptotic (caspase 3) genes in the livers of NMRI mice were examined with the use of real-time RT-PCR Array followed by exposure to an environmentally relevant and negligible cytotoxic concentration of arsenite (50 ppm) in drinking water while being fed with a high-fat diet (HFD) or low-fat diet (LFD) for 20 weeks (LFD-As and HFD-As groups). While LFD-As and HFD groups showed a decrease in BNIP3 expression, a significant increase was observed in the HFD-As group. P62 gene showed downregulation in LFD-As and HFD groups, and upregeneration was observed in the HFD-As group. Caspase 3 showed increased expression as the key factor associated with apoptotic liver cell death in the three groups, with the highest value in HFD-As group. Overall, the changes observed in the expression of Sqstm1, BNIP3, and caspase 3 in this study can be related to the level of liver damage caused by exposure to arsenic and HFD and probably, BNIP3 pro-apoptotic protein is associated with an increased cell death due to HFD and As.

Molecular mechanism and research progress on pharmacology of traditional Chinese medicine in liver injury

CONTEXT

Liver disease is a common threat to human health, caused by a variety of factors that damage the liver. Recent studies have shown that active ingredients (for example: flavonoids, saponins, acids, phenols, and alkaloids) from Traditional Chinese Medicine (TCM) can have hepatoprotective benefits, which represents an attractive source of drug discovery for treating liver injury.

OBJECTIVE

We reviewed recent contributions on the chemically induced liver injury, immunological liver damage, alcoholic liver injury, and drug-induced liver injury, in order to summarize the research progress in molecular mechanism and pharmacology of TCM, and provides a comprehensive overview of new TCM treatment strategies for liver disease.

MATERIALS AND METHODS

Relevant literature was obtained from scientific databases such as Pubmed, Web of Science. and CNKI databases on ethnobotany and ethnomedicines (from January 1980 to the end of May 2018). The experimental studies involving the antihepatic injury role of the active agents from TCM and the underlying mechanisms were identified. The search terms included 'liver injury' or 'hepatic injury', and 'traditional Chinese medicine', or 'herb'.

RESULTS

A number of studies revealed that the active ingredients of TCM exhibit potential therapeutic benefits against liver injury, while the underlying mechanisms appear to contribute to the regulation of inflammation, oxidant stress, and pro-apoptosis signaling pathways.

DISCUSSION AND CONCLUSIONS

The insights provided in this review will help further exploration of botanical drugs in the development of liver injury therapy via study on the effective components of TCM.

RIPK3-Mediated Necroptosis and Neutrophil Infiltration Are Associated with Poor Prognosis in Patients with Alcoholic Cirrhosis

Alcoholic cirrhosis is an end-stage liver disease with impaired survival and often requires liver transplantation. Recent data suggests that receptor-interacting protein kinase-3- (RIPK3-) mediated necroptosis plays an important role in alcoholic cirrhosis. Additionally, neutrophil infiltration is the most characteristic pathologic hallmark of alcoholic hepatitis. Whether RIPK3 level is correlated with neutrophil infiltration or poor prognosis in alcoholic cirrhotic patients is still unknown. We aimed to determine the correlation of RIPK3 and neutrophil infiltration with the prognosis in the end-stage alcoholic cirrhotic patients. A total of 20 alcoholic cirrhotic patients subjected to liver transplantation and 5 normal liver samples from control patients were retrospectively enrolled in this study. Neutrophil infiltration and necroptosis were assessed by immunohistochemical staining for myeloperoxidase (MPO) and RIPK3, respectively. The noninvasive score system (model for end-stage liver disease (MELD)) and histological score systems (Ishak, Knodell, and ALD grading and ALD stage) were used to evaluate the prognosis. Neutrophil infiltration was aggravated in patients with a high MELD score (≥32) in the liver. The MPO and RIPK3 levels in the liver were positively related to the Ishak score. The RIPK3 was also significantly and positively related to the Knodell score. In conclusion, RIPK3-mediated necroptosis and neutrophil-mediated alcoholic liver inflammatory response are highly correlated with poor prognosis in patients with end-stage alcoholic cirrhosis. RIPK3 and MPO might serve as potential predictors for poor prognosis in alcoholic cirrhotic patients.

A Unifying Hypothesis Linking Hepatic Adaptations for Ethanol Metabolism to the Proinflammatory and Profibrotic Events of Alcoholic Liver Disease

The pathogenesis of alcoholic liver disease (ALD) remains poorly understood but is likely a multihit pathophysiological process. Here, we propose a hypothesis of how early mitochondrial adaptations for alcohol metabolism lead to ALD pathogenesis. Acutely, ethanol (EtOH) feeding causes a near doubling of hepatic EtOH metabolism and oxygen consumption within 2 to 3 hours. This swift increase in alcohol metabolism (SIAM) is an adaptive response to hasten metabolic elimination of both EtOH and its more toxic metabolite, acetaldehyde (AcAld). In association with SIAM, EtOH causes widespread hepatic mitochondrial depolarization (mtDepo), which stimulates oxygen consumption. In parallel, voltage-dependent anion channels (VDAC) in the mitochondrial outer membrane close. Together, VDAC closure and respiratory stimulation promote selective and more rapid oxidation of EtOH first to AcAld in the cytosol and then to nontoxic acetate in mitochondria, since membrane-permeant AcAld does not require VDAC to enter mitochondria. VDAC closure also inhibits mitochondrial fatty acid oxidation and ATP release, promoting steatosis and a decrease in cytosolic ATP. After acute EtOH, these changes revert as EtOH is eliminated with little hepatocellular cytolethality. mtDepo also stimulates mitochondrial autophagy (mitophagy). After chronic high EtOH exposure, the capacity to process depolarized mitochondria by mitophagy becomes compromised, leading to intra- and extracellular release of damaged mitochondria, mitophagosomes, and/or autolysosomes containing mitochondrial damage-associated molecular pattern (mtDAMP) molecules. mtDAMPs cause inflammasome activation and promote inflammatory and profibrogenic responses, causing hepatitis and fibrosis. We propose that persistence of mitochondrial responses to EtOH metabolism becomes a tipping point, which links initial adaptive EtOH metabolism to maladaptive changes initiating onset and progression of ALD.

β-Arrestin 2 Promotes Hepatocyte Apoptosis by Inhibiting Akt Pathway in Alcoholic Liver Disease

Alcoholic liver disease (ALD) is a complex process that includes a wide range of hepatic lesions, from steatosis to cirrhosis, and even hepatocellular carcinoma (HCC). Accumulating evidence shows that the cytotoxic effects of ethanol metabolism lead to cell apoptosis and necrosis in ALD. Recently, several studies revealed that multifunctional protein β-arrestin 2 (Arrb2) modulated cell apoptosis in liver fibrosis and HCC, but its role in ALD has not been fully understood. The aim of this study is to explore the function and underlying mechanism of Arrb2 in hepatocyte survival and apoptosis in ALD. In our study, the primary hepatocytes were isolated from the livers of C57BL/6 mice fed EtOH-containing diet, it showed an increased level of Arrb2. EtOH also significantly up-regulated Arrb2 production in AML-12 cells in vitro. Furthermore, TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) and FCM results demonstrated that knockdown of Arrb2 could inhibit hepatocyte apoptosis induced by EtOH in vivo and vitro while over-expression of Arrb2 induced apoptosis in ALD. In addition, western blot results revealed that Arrb2 remarkably suppressed the Akt signaling. Taken together, our data suggested that Arrb2 may serve as a potential therapeutic target for ALD by promoting hepatocyte apoptosis via Akt suppression.

Alcoholic liver disease

Alcoholic liver disease (ALD) is the most prevalent type of chronic liver disease worldwide. ALD can progress from alcoholic fatty liver (AFL) to alcoholic steatohepatitis (ASH), which is characterized by hepatic inflammation. Chronic ASH can eventually lead to fibrosis and cirrhosis and in some cases hepatocellular cancer (HCC). In addition, severe ASH (with or without cirrhosis) can lead to alcoholic hepatitis, which is an acute clinical presentation of ALD that is associated with liver failure and high mortality. Most individuals consuming >40 g of alcohol per day develop AFL; however, only a subset of individuals will develop more advanced disease. Genetic, epigenetic and non-genetic factors might explain the considerable interindividual variation in ALD phenotype. The pathogenesis of ALD includes hepatic steatosis, oxidative stress, acetaldehyde-mediated toxicity and cytokine and chemokine-induced inflammation. Diagnosis of ALD involves assessing patients for alcohol use disorder and signs of advanced liver disease. The degree of AFL and liver fibrosis can be determined by ultrasonography, transient elastography, MRI, measurement of serum biomarkers and liver biopsy histology. Alcohol abstinence achieved by psychosomatic intervention is the best treatment for all stages of ALD. In the case of advanced disease such as cirrhosis or HCC, liver transplantation may be required. Thus, new therapies are urgently needed.

Role of aldehyde dehydrogenase 2 in ischemia reperfusion injury: An update

Aldehyde dehydrogenase 2 (ALDH2) is best known for its critical detoxifying role in liver alcohol metabolism. However, ALDH2 dysfunction is also involved in a wide range of human pathophysiological situations and is associated with complications such as cardiovascular diseases, diabetes mellitus, neurodegenerative diseases and aging. A growing body of research has shown that ALDH2 provides important protection against oxidative stress and the subsequent loading of toxic aldehydes such as 4-hydroxy-2-nonenal and adducts that occur in human diseases, including ischemia reperfusion injury (IRI). There is increasing evidence of its role in IRI pathophysiology in organs such as heart, brain, small intestine and kidney; however, surprisingly few studies have been carried out in the liver, where ALDH2 is found in abundance. This study reviews the role of ALDH2 in modulating the pathways involved in the pathophysiology of IRI associated with oxidative stress, autophagy and apoptosis. Special emphasis is placed on the role of ALDH2 in different organs, on therapeutic “preconditioning” strategies, and on the use of ALDH2 agonists such as Alda-1, which may become a useful therapeutic tool for preventing the deleterious effects of IRI in organ transplantation.

SNX10 mediates alcohol-induced liver injury and steatosis by regulating the activation of chaperone-mediated autophagy

BACKGROUND & AIMS

Alcoholic liver disease (ALD) is a major cause of morbidity and mortality worldwide. However, the cellular defense mechanisms underlying ALD are not well understood. Recent studies highlighted the involvement of chaperone-mediated autophagy (CMA) in regulating hepatic lipid metabolism. Sorting nexin (SNX)-10 has a regulatory function in endolysosomal trafficking and stabilisation. Here, we investigated the roles of SNX10 in CMA activation and in the pathogenesis of alcohol-induced liver injury and steatosis.

METHODS

Snx10 knockout (Snx10 KO) mice and their wild-type (WT) littermates fed either the Lieber-DeCarli liquid alcohol diet or a control liquid diet, and primary cultured WT and Snx10 KO hepatocytes stimulated with ethanol, were used as in vivo and in vitro ALD models, respectively. Activation of CMA, liver injury parameters, inflammatory cytokines, oxidative stress and lipid metabolism were measured.

RESULTS

Compared with WT littermates, Snx10 KO mice exhibited a significant amelioration in ethanol-induced liver injury and hepatic steatosis. Both in vivo and in vitro studies showed that SNX10 deficiency upregulated lysosome-associated membrane protein type 2A (LAMP-2A) expression and CMA activation, which could be reversed by SNX10 overexpression in vitro. LAMP-2A interference confirmed that the upregulation of Nrf2 and AMPK signalling pathways induced by SNX10 deficiency relied on CMA activation. Pull-down assays revealed an interaction between SNX10 and cathepsin A (CTSA), a key enzyme involved in LAMP-2A degradation. Deficiency in SNX10 inhibited CTSA maturation and increased the stability of LAMP-2A, resulting in an increase in CMA activity.

CONCLUSIONS

SNX10 controls CMA activity by mediating CTSA maturation, and, thus, has an essential role in alcohol-induced liver injury and steatosis. Our results provide evidence for SNX10 as a potential promising therapeutic target for preventing or ameliorating liver injury in ALD.

LAY SUMMARY

Alcoholic liver disease is a major cause of morbidity and mortality worldwide. Recent studies highlight the involvement of chaperone-mediated autophagy (CMA) in regulating hepatic lipid metabolism. Our study reveals that deficiency of sorting nexin (SNX) 10 increases the stability of LAMP-2A by inhibiting cathepsin A maturation, resulting in the increase of CMA activity and, thus, alleviates alcohol-induced liver injury and steatosis.

Endocrine Adiponectin-FGF15/19 Axis in Ethanol-Induced Inflammation and Alcoholic Liver Injury

Alcoholic liver disease (ALD) is the most prevalent form of liver disease, encompassing a spectrum of progressive pathological changes from steatosis to steatohepatitis to fibrosis/cirrhosis and hepatocellular carcinoma. Alcoholic steatosis/steatohepatitis is the initial stage of ALD and a major risk factor for advanced liver injuries. Adiponectin is a hormone secreted from adipocytes. Fibroblast growth factor (FGF) 15 (human homolog, FGF19) is an ileum-derived hormone. Adipocyte-derived adiponectin and gut-derived FGF15/19 regulate each other, share common signaling cascades, and exert similar beneficial functions. Emerging evidence has revealed that dysregulated adiponectin-FGF15/19 axis and impaired hepatic adiponectin-FGF15/19 signaling are associated with alcoholic liver damage in rodents and humans. More importantly, endocrine adiponectin-FGF15/19 signaling confers protection against ethanol-induced liver damage via fine tuning the adipose-intestine-liver crosstalk, leading to limited hepatic inflammatory responses, and ameliorated alcoholic liver injury. This review is focused on the recently discovered endocrine adiponectin-FGF15/19 axis that is emerging as an essential adipose-gut-liver coordinator involved in the development and progression of alcoholic steatohepatitis.

Pyroptosis by caspase11/4-gasdermin-D pathway in alcoholic hepatitis in mice and patients

Alcoholic hepatitis (AH) continues to be a disease with high mortality and no efficacious medical treatment. Although severe AH is presented as acute on chronic liver failure, what underlies this transition from chronic alcoholic steatohepatitis (ASH) to AH is largely unknown. To address this question, unbiased RNA sequencing and proteomic analyses were performed on livers of the recently developed AH mouse model, which exhibits the shift to AH from chronic ASH upon weekly alcohol binge, and these results are compared to gene expression profiling data from AH patients. This cross-analysis has identified Casp11 (CASP4 in humans) as a commonly up-regulated gene known to be involved in the noncanonical inflammasome pathway. Immunoblotting confirms CASP11/4 activation in AH mice and patients, but not in chronic ASH mice and healthy human livers. Gasdermin-D (GSDMD), which induces pyroptosis (lytic cell death caused by bacterial infection) downstream of CASP11/4 activation, is also activated in AH livers in mice and patients. CASP11 deficiency reduces GSDMD activation, bacterial load in the liver, and severity of AH in the mouse model. Conversely, the deficiency of interleukin-18, the key antimicrobial cytokine, aggravates hepatic bacterial load, GSDMD activation, and AH. Furthermore, hepatocyte-specific expression of constitutively active GSDMD worsens hepatocellular lytic death and polymorphonuclear leukocyte inflammation.

CONCLUSION

These results implicate pyroptosis induced by the CASP11/4-GSDMD pathway in the pathogenesis of AH. (Hepatology 2018;67:1737-1753).

MicroRNA-200a induces apoptosis by targeting ZEB2 in alcoholic liver disease

ABSTRAT Alcoholic liver disease (ALD) and its complication continued to be a major health problem throughout the world. Increasing evidence suggests that microRNA (miRNA) that regulate apoptosis, inflammation and lipid metabolism are affected by alcohol in ALD. MiR-200a has emerged as a major regulator in several liver diseases, but its role in ALD has not been elucidated. The aim of this study is to figure out the biological function of miR-200a in ALD and to explore its underlying mechanism. The expression pattern of miR-200a were analyzed in vitro and in vivo, we showed that miR-200a was up-regulated in ALD in AML-12 and primary hepatocyte. We then examined it's effect on cell apoptosis and identified zinc finger E-box binding homeobox 2 (ZEB2; also known as SIP1) as a direct target gene of miR-200a. Furthermore, reintroduction of ZEB2 could reverse the pro-apoptosis of miR-200a on AML-12. Taken together, our study demonstrated that miR-200a regulates the apoptosis of hepatocyte in ALD by directly target ZEB2, both of which could serve as new therapeutic targets for ALD.

Multifaceted Roles of GSK-3 in Cancer and Autophagy-Related Diseases

GSK-3 is a ubiquitously expressed serine/threonine kinase existing as GSK-3α and GSK-3β isoforms, both active under basal conditions and inactivated upon phosphorylation by different upstream kinases. Initially discovered as a regulator of glycogen synthesis, GSK-3 is also involved in several signaling pathways controlling many different key functions. Here, we discuss recent advances regarding (i) GSK-3 structure, function, regulation, and involvement in several cancers, including hepatocarcinoma, cholangiocarcinoma, breast cancer, prostate cancer, leukemia, and melanoma (active GSK-3 has been shown to induce apoptosis in some cases or inhibit apoptosis in other cases and to induce cancer progression or inhibit tumor cell proliferation, suggesting that different GSK-3 modulators may address different specific targets); (ii) GSK-3 involvement in autophagy modulation, reviewing signaling pathways involved in neurodegenerative and liver diseases; (iii) GSK-3 role in oxidative stress and autophagic cell death, focusing on liver injury; (iv) GSK-3 as a possible therapeutic target of natural substances and synthetic inhibitors in many diseases; and (v) GSK-3 role as modulator of mammalian aging, related to metabolic alterations characterizing senescent cells and age-related diseases. Studies summarized here underline the GSK-3 multifaceted role and indicate such kinase as a molecular target in different pathologies, including diseases associated with autophagy dysregulation.

Root bark of Ulmus davidiana var. japonica restrains acute alcohol-induced hepatic steatosis onset in mice by inhibiting ROS accumulation

Alcohol-induced hepatic steatosis and inflammation are key drivers of alcohol-induced liver injury, mainly caused by oxidative stress. The roots bark of Ulmus davidiana var. japonica is well known for its substantial antioxidative and antitumorigenic potency. In this study, we examined whether this plant can ameliorate alcohol-induced liver injuries characterized by hepatic steatosis and inflammation through its antioxidative activity. C57BL/6J mice were treated with the root bark extract of Ulmus davidiana var. japonica (RUE; 100 mg of extract/kg bodyweight; oral gavage) and alcohol (1 g/kg of bodyweight; oral gavage) for 5 days. Markers of acute alcohol-induced hepatic steatosis were determined and putative molecular mechanisms responsible for the protection of RUE were investigated. RUE noticeably protected against alcohol-induced hepatic steatosis and inflammation. Reactive oxygen species (ROS), over-produced by alcohol, negatively orchestrated various signaling pathways involved in the lipid metabolism and inflammation. These pathways were restored through the ROS scavenging activity of RUE in the liver. In particular, the expression of lipogenic genes (e.g., SREBP-1, ACC, and FAS) and inflammatory cytokines (e.g., IL-1β, and NF-κB p65) significantly decreased with RUE treatment. Conversely, the expression of fatty acid oxidation-related genes (e.g., SIRT1, AMPKα, and PGC1α) were increased in mice treated with RUE. Thus, the results indicate that RUE counteracts and thus attenuates alcoholic hepatic steatosis onset in mice, possibly by suppressing ROS-mediated steatosis and inflammation.

Animal Models of Alcoholic Liver Disease: Pathogenesis and Clinical Relevance

Alcoholic liver disease (ALD), a leading cause of chronic liver injury worldwide, comprises a range of disorders including simple steatosis, steatohepatitis, cirrhosis, and hepatocellular carcinoma. Over the last five decades, many animal models for the study of ALD pathogenesis have been developed. Recently, a chronic-plus-binge ethanol feeding model was reported. This model induces significant steatosis, hepatic neutrophil infiltration, and liver injury. A clinically relevant model of high-fat diet feeding plus binge ethanol was also developed, which highlights the risk of excessive binge drinking in obese/overweight individuals. All of these models recapitulate some features of the different stages of ALD and have been widely used by many investigators to study the pathogenesis of ALD and to test for therapeutic drugs/components. However, these models are somewhat variable, depending on mouse genetic background, ethanol dose, and animal facility environment. This review focuses on these models and discusses these variations and some methods to improve the feeding protocol. The pathogenesis, clinical relevance, and translational studies of these models are also discussed.

Autophagy in the liver: functions in health and disease

The concept of macroautophagy was established in 1963, soon after the discovery of lysosomes in rat liver. Over the 50 years since, studies of liver autophagy have produced many important findings. The liver is rich in lysosomes and possesses high levels of metabolic-stress-induced autophagy, which is precisely regulated by concentrations of hormones and amino acids. Liver autophagy provides starved cells with amino acids, glucose and free fatty acids for use in energy production and synthesis of new macromolecules, and also controls the quality and quantity of organelles such as mitochondria. Although the efforts of early investigators contributed markedly to our current knowledge of autophagy, the identification of autophagy-related genes represented a revolutionary breakthrough in our understanding of the physiological roles of autophagy in the liver. A growing body of evidence has shown that liver autophagy contributes to basic hepatic functions, including glycogenolysis, gluconeogenesis and β-oxidation, through selective turnover of specific cargos controlled by a series of transcription factors. In this Review, we outline the history of liver autophagy study, and then describe the roles of autophagy in hepatic metabolism under healthy and disease conditions, including the involvement of autophagy in α1-antitrypsin deficiency, NAFLD, hepatocellular carcinoma and viral hepatitis.

Effect of shikonin on concanavalin A-induced liver injury and possible mechanisms involved

AIM

To investigate the effect of shikonin on concanavalin A (Con A)-induced acute liver injury in mice and explore the underlying mechanisms.

METHODS

Acute liver injury was induced by Con A in Balb/c mice through tail injection. The mice were randomly divided into five groups of fourteen mice as follows: (1) normal group; (2) Con A-induced model group; (3) low-dose (12.5 mg/kg) shikonin + Con A group; (4) medium-dose (25 mg/kg) shikonin + Con A group; (5) high-dose (50 mg/kg) shikonin + Con A group. Histological grading and the measurement of the levels of alanine transaminase (ALT), aspartate transaminase (AST), nitric oxide (NO), inducible nitric oxide synthase (iNOS), nuclear factor-κB (NF-κB), IκBα and IκBβ were performed.

RESULTS

Compared to the normal group, the histological grade as well as the levels of ALT, AST, NO, iNOS and NF-κB significantly increased in the model group, but the levels of IκBα and IκBβ were decreased. After shikonin (50 mg/kg) treatment, the histological grade and the levels of ALT, AST, NO, iNOS and NF-κB significantly were decreased, and the levels of IκBα and IκBβ were increased. The doses of 12.5 mg/kg and 25 mg/kg worked inefficiently.

CONCLUSION

Shikonin (50 mg/kg) protects against Con A-induced liver injury by decreasing the level of NO, which may correlate with the amelioration of NF-κB activity.