Mechanisms of alcohol-induced hepatic fibrosis: a summary of the Ron Thurman Symposium

Effects of idebenone and coenzyme Q10 on NLRP3/caspase-1/IL-1β pathway regulation on ethanol-induced hepatotoxicity in rats

Chronic and excessive alcohol consumption leads to liver toxicity. There is a need to investigate effective therapeutic strategies to alleviate alcohol-induced liver injury, which remains the leading cause of liver-related morbidity and mortality worldwide. Therefore here, we looked into and evaluated how ethanol-induced hepatotoxicity was affected by coenzyme Q10 (CoQ10) and its analog, idebenone (IDE), on the NLRP3/caspase-1/IL-1 pathway. Hepatotoxicity induced in rats through the oral administration of gradually increasing dosages of ethanol (from 2 to 6 g/kg/day) over 30 days and the effect of CoQ10 (10 or 20 mg/kg) and IDE (50 or 100 mg/kg) were evaluated. Serum hepatotoxicity markers (ALT, AST, GGT, ALP, and TBIL), tissue oxidative stress markers and the mRNA expressions of IL-1β, IL-18, TGF-β, NF-κB, NLRP3, and caspase-1 were evaluated. Masson's trichrome staining was also used to visualize fibrosis in the liver tissue. The results indicated that ethanol exposure led to hepatotoxicity as well as considerable NLRP3/caspase-1/IL-1β pathway activation. Moreover, CoQ10 or IDE treatment reduced measured parameters in a dosage-dependent manner. Thus, by inhibiting the NLRP3/caspase-1/IL-1 pathway, CoQ10 and IDE can prevent the hepatotoxicity caused by ethanol, although CoQ10 is more effective than IDE. This study will provide insight into new therapeutic avenues that take advantage of the anti-inflammatory and antioxidant properties of CoQ10 and IDE in ethanol-induced liver diseases.

Impact of alcohol consumption on metabolic dysfunction-associated fatty liver disease development and remission: A longitudinal cohort study

BACKGROUND

The influence of alcohol intake on metabolic dysfunction-associated fatty liver disease (MAFLD) development and remission remains unclear; thus, we aimed to investigate their longitudinal associations.

METHODS

This observational cohort study included 6349 patients who underwent more than two health check-ups over >2 years between April 2013 and March 2021. Generalized estimation equations were used to analyse the longitudinal associations between changes in alcohol intake and MAFLD according to repeated measures at baseline and the most recent stage.

RESULTS

The MAFLD development and remission rates were 20.4 and 5.1 and 9.1 and 4.7% in men and women, respectively. Although alcohol consumption was not a significant factor for MAFLD development, consuming 0.1-69.9 g/week (odds ratio [OR]: 0.672, 95% confidence interval [CI]: 0.469-0.964, p < .05) and ≥280 g/week were significant factors for MAFLD development in males (OR: 1.796, 95% CI: 1.009-3.196, p < .05) and females (OR: 16.74, 95% CI: 3.877-72.24, p < .001). Regardless of quantity and frequency, alcohol consumption was not a significant factor for MAFLD remission. Several noninvasive liver fibrosis scores were significantly associated with alcohol intake quantity and frequency in males with MAFLD development and remission (p < .05). The nonalcoholic fatty liver disease fibrosis score differed significantly between males with and without reduced alcohol intake (p < .05) who showed MAFLD remission.

CONCLUSIONS

Although the influence of alcohol intake on MAFLD development and remission differed, alcohol consumption was not beneficial for MAFLD remission in either sex. Alcohol intake reduction or cessation is recommended to prevent liver fibrosis, even in those who achieve MAFLD remission.

Endotoxin Inflammatory Action on Cells by Dysregulated-Immunological-Barrier-Linked ROS-Apoptosis Mechanisms in Gut-Liver Axis

Our study highlighted the immune changes by pro-inflammatory biomarkers in the gut-liver-axis-linked ROS-cell death mechanisms in chronic and acute inflammations when gut cells are exposed to endotoxins in patients with hepatic cirrhosis or steatosis. In duodenal tissue samples, gut immune barrier dysfunction was analyzed by pro-inflammatory biomarker expressions, oxidative stress, and cell death by flow cytometry methods. A significant innate and adaptative immune system reaction was observed as result of persistent endotoxin action in gut cells in chronic inflammation tissue samples recovered from hepatic cirrhosis with the A-B child stage. Instead, in patients with C child stage of HC, the endotoxin tolerance was installed in cells, characterized by T lymphocyte silent activation and increased Th1 cytokines expression. Interesting mechanisms of ROS-cell death were observed in chronic and acute inflammation samples when gut cells were exposed to endotoxins and immune changes in the gut-liver axis. Late apoptosis represents the chronic response to injury induction by the gut immune barrier dysfunction, oxidative stress, and liver-dysregulated barrier. Meanwhile, necrosis represents an acute and severe reply to endotoxin action on gut cells when the immune system reacts to pro-inflammatory Th1 and Th2 cytokines releasing, offering protection against PAMPs/DAMPs by monocytes and T lymphocyte activation. Flow cytometric analysis of pro-inflammatory biomarkers linked to oxidative stress-cell death mechanisms shown in our study recommends laboratory techniques in diagnostic fields.

Aldehyde Dehydrogenase 2 (ALDH2) Deficiency, Obesity, and Atrial Fibrillation Susceptibility: Unraveling the Connection

Atrial fibrillation (AF), characterized by structural remodeling involving atrial myocardial degradation and fibrosis, is linked with obesity and transforming growth factor beta 1 (TGF-β1). Aldehyde dehydrogenase 2 (ALDH2) deficiency, highly prevalent in East Asian people, is paradoxically associated with a lower AF risk. This study investigated the impact of ALDH2 deficiency on diet-induced obesity and AF vulnerability in mice, exploring potential compensatory upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme-oxygenase 1 (HO-1). Wild-type (WT) and ALDH2*2 knock-in (KI) mice were administered a high-fat diet (HFD) for 16 weeks. Despite heightened levels of reactive oxygen species (ROS) post HFD, the ALDH2*2 KI mice did not exhibit a greater propensity for AF compared to the WT controls. The ALDH2*2 KI mice showed equivalent myofibril degradation in cardiomyocytes compared to WT after chronic HFD consumption, indicating suppressed ALDH2 production in the WT mice. Atrial fibrosis did not proportionally increase with TGF-β1 expression in ALDH2*2 KI mice, suggesting compensatory upregulation of the Nrf2 and HO-1 pathway, attenuating fibrosis. In summary, ALDH2 deficiency did not heighten AF susceptibility in obesity, highlighting Nrf2/HO-1 pathway activation as an adaptive mechanism. Despite limitations, these findings reveal a complex molecular interplay, providing insights into the paradoxical AF-ALDH2 relationship in the setting of obesity.

Harnessing the potential of probiotics in the treatment of alcoholic liver disorders

In the current scenario, prolonged consumption of alcohol across the globe is upsurging an appreciable number of patients with the risk of alcohol-associated liver diseases. According to the recent report, the gut-liver axis is crucial in the progression of alcohol-induced liver diseases, including steatosis, steatohepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma. Despite several factors associated with alcoholic liver diseases, the complexity of the gut microflora and its great interaction with the liver have become a fascinating area for researchers due to the high exposure of the liver to free radicals, bacterial endotoxins, lipopolysaccharides, inflammatory markers, etc. Undoubtedly, alcohol-induced gut microbiota imbalance stimulates dysbiosis, disrupts the intestinal barrier function, and trigger immune as well as inflammatory responses which further aggravate hepatic injury. Since currently available drugs to mitigate liver disorders have significant side effects, hence, probiotics have been widely researched to alleviate alcohol-associated liver diseases and to improve liver health. A broad range of probiotic bacteria like Lactobacillus, Bifidobacteria, Escherichia coli, Sacchromyces, and Lactococcus are used to reduce or halt the progression of alcohol-associated liver diseases. Several underlying mechanisms, including alteration of the gut microbiome, modulation of intestinal barrier function and immune response, reduction in the level of endotoxins, and bacterial translocation, have been implicated through which probiotics can effectively suppress the occurrence of alcohol-induced liver disorders. This review addresses the therapeutic applications of probiotics in the treatment of alcohol-associated liver diseases. Novel insights into the mechanisms by which probiotics prevent alcohol-associated liver diseases have also been elaborated.

Immune dysregulation and pathophysiology of alcohol consumption and alcoholic liver disease

Alcoholic liver disease (ALD) is a clinical-pathologic entity caused by the chronic excessive consumption of alcohol. The disease includes a broad spectrum of anomalies at the cellular and tissual level that can cause acute-on-chronic (alcoholic hepatitis) or chronic (fibrosis, cirrhosis, hepatocellular cancer) injury, having a great impact on morbidity and mortality worldwide. Alcohol is metabolized mainly in the liver. During alcohol metabolism, toxic metabolites, such as acetaldehyde and oxygen reactive species, are produced. At the intestinal level, alcohol consumption can cause dysbiosis and alter intestinal permeability, promoting the translocation of bacterial products and causing the production of inflammatory cytokines in the liver, perpetuating local inflammation during the progression of ALD. Different study groups have reported systemic inflammatory response disturbances, but reports containing a compendium of the cytokines and cells involved in the pathophysiology of the disease, from the early stages, are difficult to find. In the present review article, the role of the inflammatory mediators involved in ALD progression are described, from risky patterns of alcohol consumption to advanced stages of the disease, with the aim of understanding the involvement of immune dysregulation in the pathophysiology of ALD.

The role of acetaldehyde dehydrogenase 2 in the pathogenesis of liver diseases

Common liver tissue damage is mainly due to the accumulation of toxic aldehydes in lipid peroxidation under oxidative stress. Cumulative toxic aldehydes in the liver can be effectively metabolized by acetaldehyde dehydrogenase 2 (ALDH2), thereby alleviating various liver diseases. Notably, gene mutation of ALDH2 leads to impaired ALDH2 enzyme activity, thus aggravating the progress of liver diseases. However, the relationship and specific mechanism between ALDH2 and liver diseases are not clear. Consequently, the review explains the relationship between ALDH2 and liver diseases such as alcoholic liver disease (ALD), non-alcoholic fatty liver disease (NAFLD), liver fibrosis and hepatocellular carcinoma (HCC). In addition, this review also discusses ALDH2 as a potential therapeutic target for various liver diseases,and focuses on summarizing the regulatory mechanism of ALDH2 in these liver diseases.

P2X7 Receptor in Alcoholic Steatohepatitis and Alcoholic Liver Fibrosis

Alcoholic liver disease is one of the most common chronic liver diseases in the world. It is a liver disease caused by prolonged heavy drinking and its main clinical features are nausea, vomiting, enlargement of the liver, and jaundice. Recent studies suggest that Kupffer cell-mediated inflammatory response is a core driver in the development of alcoholic steatohepatitis and alcoholic liver fibrosis. As a danger signal, extracellular ATP activates the assembly of NLPR3 inflammasome by acting on purine P2X7 receptor, the activated NLRP3 inflammasome prompts ASC to cleave pro-cCaspase-1 into active caspase-1in KCs. Active caspase-1 promotes the conversion of pro-IL-1β to IL-1β, which further enhances the inflammatory response. Here, we briefly review the role of the P2X7R-NLRP3 inflammasome axis in the pathogenesis of alcoholic liver disease and the evolution of alcoholic steatohepatitis and alcoholic liver fibrosis. Regulation of the inflammasome axis of P2X7R-NLRP3 may be a new approach for the treatment of alcoholic liver disease.

Genetic dominance of transforming growth factor-β1 polymorphisms in chronic liver disease

Chronic liver disease (CLD) is an extremely common clinical condition accompanied by sustained inflammatory response leading to tissue damage. Transforming growth factor-β1 (TGF-β1) is known as a master immune regulator in CLDs, but the association between TGF-β1 polymorphisms and CLD risk is controversial and inconclusive, and the genetic dominance of CLDs remains unknown. In this study, the relationship between TGF-β1 polymorphisms and CLD susceptibility is systematically analyzed based on 35 eligible studies. Individuals with the TGF-β1-509 allele (TT or CT) or codon 10 allele (Pro/Pro) show an increased risk of CLDs. Subgroup analyses indicate TGF-β1-509C/T has a significant correlation with cirrhosis and chronic hepatitis C, codon 10 is associated with chronic hepatitis B occurrence, and codon 25 exhibits a relationship with autoimmune hepatitis risk. Missense mutations in G29E, A105S, D191N, and F321L of TGF-β1 are the genetic factors of HCC susceptibility. Furthermore, the TGF-β1 gene expression is significantly elevated in CLD patients, and the TGF-β1 codon 263 is located close to the region where the TGF-β1 dimerization interacts, indicating the TGF-β1 codon 263 variant may affect the secretion of TGF-β1 by altering its dimerization. Together, our findings provide new insights into the immune regulator gene TGF-β1 polymorphisms as susceptibility factors for CLD occurrence and regulators for TGF-β1 expression, which have implications for the regulation of immune factors during CLD development.

Ameliorative Impacts of Wheat Germ Oil against Ethanol-Induced Hepatic and Renal Dysfunction in Rats: Involvement of Anti-Inflammatory, Anti-Apoptotic, and Antioxidant Signaling Pathways

Wheat germ oil (WGO) is a well-known product with anti-inflammatory and antioxidant properties. The current study aimed to investigate the impacts of WGO against ethanol-induced liver and kidney dysfunction at the serum, anti-inflammatory, antioxidants and anti-apoptotic signaling pathways. Rats received saline orally as a negative control or WGO in a dose of 1.5 mL/kg (1400 mg/kg body weight orally) for 15 days. The affected group received ethanol 50% v/v 10 mL/kg (5 g/kg) body weight orally once a day for consecutive 15 days to induce hepatorenal injuries in ethanolic non-treated group. The protective group received WGO daily 1 h before ethanol administration. Serum (1.5 mL) from blood was extracted and examined for the changes in biochemical assessments in serum alkaline phosphatase (ALP), alanine aminotransferase (ALT), bilirubin, serum γ-glutamyl transpeptidase (GGT), total protein, serum albumin, butyrylcholinesterase (BChE), total cholesterol (TC), total triglyceride (TG), urea, creatinine, uric acid, potassium (K⁺), Beta-2 microglobulin (β₂M), malondialdehyde (MDA), catalase (CAT), reduced glutathione (GSH), superoxide dismutase (SOD) and aspartate aminotransferase (AST). Kidney and liver homogenate was used to measure MDA, GSH and catalase activities. Quantitative real time PCR (qRT-PCR) was used to express Nrf2 and HO-1 in liver, and NF-kB and kidney injury molecule (KIM-1) in kidneys, which are correlated with oxidative stress and inflammation. Capase-3 and Bcl2 genes were examined using immunohistochemical analysis in the kidney and liver. Ethanol administration induced significant alteration in examined liver and kidney markers (AST, ALT, GGT, ALP, total proteins, urea, creatinine and uric acid). Moreover, alcohol administration decreased antioxidant activities at serum and hepatorenal tissues (GSH, catalase and SOD), while MDA was increased as a tissue degradation marker. Inflammatory cytokines, together with genes of oxidative stress markers (Nrf2 and HO-1), were all affected. At cellular levels, apoptotic marker caspase-3 was upregulated, while antiapoptotic marker B-cell lymphoma 2 (Bcl2), was down regulated using immunohistochemical analysis. Of interest, pretreatment with WGO improved the side effects induced by ethanol on hepatic, renal biomarkers and reversed its impact on serum and tissue antioxidant parameters. Nrf2/HO-1 were upregulated, while NFk-B and KIM-1 were downregulated using real time PCR. Immune reactivities of caspase-3 and Bcl2 genes were restored in the protective group. In conclusion, WGO ameliorated ethanol-induced hepatic and renal dysfunction at the biochemical, molecular and cellular levels by regulating some mechanisms that controls oxidative stress, apoptosis, inflammation and anti-apoptotic pathways.

Joint association of alcohol consumption and adiposity with alcohol- and obesity-related cancer in a population sample of 399,575 UK adults

Obesity and alcohol consumption are both important modifiable risk factors for cancer. We examined the joint association of adiposity and alcohol consumption with alcohol- and obesity-related cancer incidence. This prospective cohort study included cancer-free UK Biobank participants aged 40-69 years. Alcohol consumption was categorised based on current UK guidelines into four groups. We defined three markers of adiposity: body fat percentage (BF %), waist circumference and BMI and categorised each into three groups. We derived a joint alcohol consumption and adiposity marker variable with twelve mutually exclusive categories. Among 399 575 participants, 17 617 developed alcohol-related cancer and 20 214 developed obesity-related cancer over an average follow-up of 11·8 (SD 0·9) years. We found relatively weak evidence of independent associations of alcohol consumption with cancer outcomes. However, the joint association analyses showed that across all adiposity markers, above guideline drinkers who were in the top two adiposity groups had elevated cancer incidence risk (e.g. HR for alcohol-related cancer was 1·53 (95 % CI (1·24, 1·90)) for within guideline drinkers and 1·61 (95 % CI (1·30, 2·00)) for above guideline drinkers among participants who were in the top tertile BF %. Regardless of alcohol consumption status, the risk of obesity-related cancer increased with higher adiposity in a dose-response manner within alcohol consumption categories. Our study provides guidance for public health priorities aimed at lowering population cancer risk via two key modifiable risk factors.

Metabolic dysfunction-associated fatty liver disease directly related to liver fibrosis independent of insulin resistance, hyperlipidemia, and alcohol intake in morbidly obese patients

AIM

Hepatic fibrosis is associated with various factors, including metabolic dysfunction-associated fatty liver disease (MAFLD), insulin resistance, and alcohol intake in patients with morbid obesity. We investigated factors directly associated with hepatic fibrosis in patients with morbid obesity using a graphical model.

METHODS

We enrolled 134 consecutive patients with morbid obesity who underwent liver biopsy during sleeve gastrectomy (median age 43.5 years; MAFLD 78.4%; homeostasis model assessment of insulin resistance [HOMA-IR] 5.97; >20 g/day alcohol intake 14.2%). Patients were classified into none/mild (F0/1; n = 77) or significant/advanced fibrosis (F2/3; n = 57) groups, based on histology. Factors associated with F2/3 were analyzed using logistic regression analysis and a graphical model.

RESULTS

F2/3 was observed in 42.5% of the enrolled patients. The prevalence of MAFLD and HOMA-IR values were significantly higher in the F2/3 group than in the F0/1 group; however, no significant difference in alcohol intake was observed between the two groups. On logistic regression analysis, MAFLD, but not HOMA-IR or alcohol intake, was the only independent factor associated with F2/3 (odds ratio 7.555; 95% confidence interval 2.235-25.544; p = 0.0011). The graphical model revealed that F2/3 directly interacted with MAFLD, diabetes mellitus, HOMA-IR, and low-density lipoprotein cholesterol. Among these factors, MAFLD showed the strongest interaction with F2/3.

CONCLUSIONS

We determined that MAFLD was more directly associated with significant/advanced fibrosis than insulin resistance or hyperlipidemia, and alcohol intake was not directly associated with hepatic fibrosis. Metabolic dysfunction-associated fatty liver disease could be the most important factor for hepatic fibrosis in patients with morbid obesity.

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.

Synergistic and Detrimental Effects of Alcohol Intake on Progression of Liver Steatosis

Nonalcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD) are the most common liver disorders worldwide and the major causes of non-viral liver cirrhosis in the general population. In NAFLD, metabolic abnormalities, obesity, and metabolic syndrome are the driving factors for liver damage with no or minimal alcohol consumption. ALD refers to liver damage caused by excess alcohol intake in individuals drinking more than 5 to 10 daily units for years. Although NAFLD and ALD are nosologically considered two distinct entities, they show a continuum and exert synergistic effects on the progression toward liver cirrhosis. The current view is that low alcohol use might also increase the risk of advanced clinical liver disease in NAFLD, whereas metabolic factors increase the risk of cirrhosis among alcohol risk drinkers. Therefore, special interest is now addressed to individuals with metabolic abnormalities who consume small amounts of alcohol or who binge drink, for the role of light-to-moderate alcohol use in fibrosis progression and clinical severity of the liver disease. Evidence shows that in the presence of NAFLD, there is no liver-safe limit of alcohol intake. We discuss the epidemiological and clinical features of NAFLD/ALD, aspects of alcohol metabolism, and mechanisms of damage concerning steatosis, fibrosis, cumulative effects, and deleterious consequences which include hepatocellular carcinoma.

Pathophysiological Aspects of Alcohol Metabolism in the Liver

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

Gut Microbiota and Chemical-Induced Acute Liver Injury

Background: Drug overdose or chemical exposures are the main causes of acute liver injury (ALI). Severe liver injury can develop into liver failure that is an important cause of liver-related mortality in intensive care units in most countries. Pharmacological studies have utilized a variety of comprehensive chemical induction models that recapitulate the natural pathogenesis of acute liver injury. Their mechanism is always based on redox imbalance-induced direct hepatotoxicity and massive hepatocyte cell death, which can trigger immune cell activation and recruitment to the liver. However, the pathogenesis of these models has not been fully stated. Many studies showed that gut microbiota plays a crucial role in chemical-induced liver injury. Hepatotoxicity is likely induced by imbalanced microbiota homeostasis, gut mucosal barrier damage, systemic immune activation, microbial-associated molecular patterns, and bacterial metabolites. Meanwhile, many preclinical studies have shown that supplementation with probiotics can improve chemical-induced liver injury. In this review, we highlight the pathogenesis of gut microorganisms in chemical-induced acute liver injury animal models and explore the protective mechanism of exogenous microbial supplements on acute liver injury.

KIR2DL2/S2 and KIR2DS5 in alcoholic cirrhotic patients undergoing liver transplantation

INTRODUCTION

The molecular mechanisms underlying alcoholic liver fibrosis and cirrhosis are not completely understood. Hepatic fibrosis involves the interplay of diverse cells and factors, including hepatic stellate cells (HSCs), Kupffer, NK cells, and T-lymphocyte subsets. Killer-cell immunoglobulin-like receptors (KIR) are membrane receptors involved in mediation between NK and activated HSCs, regulating NK cell function through their interaction with HLA-I molecules. The aim of this study was to analyse the genetic association between KIR genes and the susceptibility to or protection from alcoholic cirrhosis (AC) in a cohort of male AC patients undergoing liver transplantation (LT) with and without concomitant viral infections.

MATERIAL AND METHODS

KIR genotyping was performed in nuclear DNA extracted from 281 AC patients and compared with 319 male controls.

RESULTS

Significant differences between total AC patients and healthy controls were only found in the case of KIR2DL2 and KIR2DS5. KIR2DL2 was significantly underrepresented in non-viral AC patients (52.6% vs. 63.3%; p = 0.015), while patients heterozygous for KIR2DL2 were also underrepresented in the non-viral AC group compared with controls (p = 0.034). KIR2DS5 was overrepresented in this group compared with healthy controls (p = 0.002). All these observations were only evident in AC patients older than 54 years old.

CONCLUSIONS

Our data suggest a contrary effect of KIR2DL2 and KIR2DS5 in AC patients older than 54 years, in whom the presence of KIR2DL2 appears to be protective against AC, whereas the presence of KIR2DS5 seems to promote the fibrotic process, particularly in patients with no associated viral infection.

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.

Emodin in Rheum undulatum inhibits oxidative stress in the liver via AMPK with Hippo/Yap signalling pathway

Context: Emodin is a compound in Rheum undulatum Linne (Polygonaceae) that has been reported to exert anti-inflammatory, antibacterial, and antiallergic effects.Objective: Oxidative stress is a causative agent of liver inflammation that may lead to fibrosis and hepato-carcinoma. In this study, we investigated the antioxidant effects of emodin and its mechanism.Materials and methods: We used the hepatocyte stimulated by arachidonic acid (AA) + iron cotreatment and the C57B/6 mice orally injected with acetaminophen (APAP, 500 mg/kg, 6 h), as assessed by immunoblot and next generation sequencing (NGS). Emodin was pre-treated in hepatocyte (3 ∼ 30 μM) for 1 h before AA + iron, and in mice (10 and 30 m/kg, P.O.) for 3 days before APAP.Results: In vitro, emodin treatment inhibited the cell death induced by AA + iron maximally at a dose of 10 μM (EC₅₀ > 3 μM). In addition, emodin attenuated the decrease of anti-apoptotic proteins, and restored mitochondria membrane potential as mediated by the liver kinase B1 (LKB1)-AMP-activated protein kinase (AMPK) pathway. LKB1 mediated AMPK activation was verified using the LKB1 deficient cell line, HeLa. Emodin (10 μM; after 10 min) also induced the phosphorylation of Yes-associated protein 1 (YAP1), the main downstream target of the Hippo signalling pathway that mediated oxidative stress or the ROS-initiated signalling pathway. In vivo, the oral treatment of emodin (10 and 30 m/kg, 3 days) decreased APAP-induced hepatic damage, as indicated by decreases in antioxidant genes as well as tissue damage.Conclusion: Our results show that emodin inhibits oxidative liver injury via the AMPK/YAP mediated pathway.

The Prebiotic-Like Effects of Coprinus comatus Polysaccharides on Gut Microbiota in Normal Mice and Those with Acute Alcoholic Liver Injury: A Comparative Study

This study aims to investigate the prebiotic-like effects of Coprinus comatus polysaccharides (CCP) on gut microbiota. Mice were divided into four groups: normal group (NG), alcohol group (AG), polysaccharides group (PG), and alcohol + polysaccharides group (APG). The gut microbiota structure of feces was analyzed by determining the V3-V4 region sequence in 16S rDNA. The results showed CCP could increase the diversity of gut microbiota. Compared with NG, PG had a significantly higher relative abundance of Firmicutes and Lactobacillaceae and a lower abundance of Rikenellaceae. These changes in gut microbiota result in positive effects on gut due to a series of prebiotic-like effects of CCP. At the same time, CCP could improve some adverse changes in gut microbiota caused by acute alcohol intake, such as the increased proportion of Firmicutes, Bacteroidetes, Muribaculaceae, and Lachnospiraceae and the decreased proportion of Rikenellaceae. In conclusion, the CCP has certain prebiotic effects not only on normal mice but also on mice with acute alcoholic liver injury.

Emerging Roles of SIRT1 in Alcoholic Liver Disease

Alcoholic liver disease (ALD) is the most prevalent type of chronic liver disease worldwide with a wide spectrum of liver pathologies ranging from simple steatosis to steatohepatitis, cirrhosis, and even hepatocellular carcinoma. It has been demonstrated that ALD is mediated in whole or in part by a central signaling molecule sirtuin 1 (SIRT1), a conserved class III histone deacetylase.SIRT1 plays beneficial roles in regulating hepatic lipid metabolism, inhibiting hepatic inflammation, controlling hepatic fibrosis and mediating hepatocellular carcinoma in ALD. However, underlying molecular mechanisms are complex and remain incompletely understood. The aim of this review was to highlight the latest advances in understanding of SIRT1 regulatory mechanisms in ALD and discuss their unique potential role as novel therapeutic target for ALD treatment.

Aldehyde Dehydrogenase 2 Ameliorates Chronic Alcohol Consumption-Induced Atrial Fibrillation through Detoxification of 4-HNE

Aldehyde dehydrogenase 2 (ALDH2) is an enzyme that detoxifies reactive oxygen species (ROS)-generated aldehyde adducts such as 4-hydroxy-trans-2-nonenal (4-HNE). Previous meta-analyses have shown an increase in the risk of atrial fibrillation (AF) in patients with chronic alcohol consumption. ALDH2*2, a common dysfunctional polymorphism in the ALDH2 gene, has been linked to an increased risk of cancer and heart disease. We tested the effect of ALDH2 deficiency on alcohol-induced AF in a murine model of chronic-binge ethanol feeding, with ALDH2*2 knock-in (KI) mice generated by a CRISPR/CAS9 system. In addition, right atrial appendages were obtained from eight patients with AF undergoing open heart surgery. The results showed that burst atrial pacing induced a greater susceptibility to AF in ALDH2*2 KI mice exposed to chronic ethanol intoxication than in wild-type mice, resulting from a higher degree of 4-HNE accumulation and collagen deposition in their atria. Alda-1 attenuated transforming growth factor beta 1 (TGF-β1) expression and collagen deposition in the atria and reduced AF inducibility. Patients with AF and the ALDH2*2 allele exhibited greater oxidative stress and substrate remodeling in their atria than non-carriers. In conclusion, ALDH2 deficiency may increase the risk of chronic alcohol and tachypacing-induced AF through the accumulation of 4-HNE and increased ROS production.

Zinc Deficiency Induces Oxidative Damage and Causes Spleen Fibrosis

Zinc (Zn) is an essential trace element for animals. Zn controls the action of more than 300 enzymes and plays an important role in the regulation of gene expression. Evidence has shown that Zn has an antioxidant function, and oxidative damage can occur with Zn deficiency. To assess the effect of Zn deficiency-induced spleen fibrosis, Zn-deficient mice, normal mice, and high-Zn mice were generated and assessed. The Zn content of the spleen in each group was determined, and histopathological examination of the spleens of each group was performed. In the film, we found that the spleens of the Zn-deficient group had high levels of proteinaceous material exudation, interstitial broadening, and lymphocyte reduction, with increased collagen, α-SMA expression, antioxidants, and oxygen free radicals. Zn deficiency inhibited the expression of antioxidants in mice, and the activity of oxygen free radicals in Zn-deficient mice was increased. The detection of α-SMA, collagen 1, and TGF-β by fluorescence quantitative PCR revealed that the expression index increased in Zn-deficient mice. In addition, to verify the effect of Zn deficiency on the extracellular matrix (ECM) regulatory system, MMPs were determined by real-time PCR, and the expression in the Zn deficiency group was lower than that in the normal group and high-Zn group. The MMP-2 and MMP-13 analyses showed that the expression of the high-Zn group was significantly higher than that of the normal group, indicating that Zn plays an important role in its expression. The above experimental analysis showed that Zn deficiency induces oxygen free radical damage, which further leads to spleen fibrosis.

Aldehyde Dehydrogenase, Liver Disease and Cancer

Acetaldehyde dehydrogenase 2 (ALDH2) is the key enzyme responsible for metabolism of the alcohol metabolite acetaldehyde in the liver. In addition to conversion of the acetaldehyde molecule, ALDH is also involved in other cellular functions. Recently, many studies have investigated the involvement of ALDH expression in viral hepatitis, alcoholic liver disease (ALD), non-alcoholic fatty liver disease (NAFLD), liver fibrosis, and liver cancer. Notably, ALDH2 expression has been linked with liver cancer risk, as well as pathogenesis and prognosis, and has emerged as a promising therapeutic target. Of note, approximately 8% of the world's population, and approximately 30-40% of the population in East Asia carry an inactive ALDH2 gene. This review summarizes new progress in understanding tissue-specific acetaldehyde metabolism by ALDH2 as well as the association of ALDH2 gene polymorphisms with liver disease and cancer. New research directions emerging in the field are also briefly discussed.

Effects of Food Processing on In Vivo Antioxidant and Hepatoprotective Properties of Green Tea Extracts

Food processing can affect the nutrition and safety of foods. A previous study showed that tannase and ultrasound treatment could significantly increase the antioxidant activities of green tea extracts according to in vitro evaluation methods. Since the results from in vitro and in vivo experiments may be inconsistent, the in vivo antioxidant activities of the extracts were studied using a mouse model of alcohol-induced acute liver injury in this study. Results showed that all the extracts decreased the levels of aspartate transaminase and alanine aminotransferase in serum, reduced the levels of malondialdehyde and triacylglycerol in the liver, and increased the levels of catalase and glutathione in the liver, which can alleviate hepatic oxidative injury. In addition, the differences between treated and original extracts were not significant in vivo. In some cases, the food processing can have a negative effect on in vivo antioxidant activities. That is, although tannase and ultrasound treatment can significantly increase the antioxidant activities of green tea extracts in vitro, it cannot improve the in vivo antioxidant activities, which indicates that some food processing might not always have positive effects on products for human benefits.

Nimbolide ameliorates unilateral ureteral obstruction-induced renal fibrosis by inhibition of TGF-β and EMT/Slug signalling

Chronic kidney disease (CKD) involves interstitial fibrosis as an underlying pathological process associated with compromised renal function irrespective of etiological cause of the injury. The transforming growth factor-β (TGF-β) plays a pivotal role in progression of renal fibrosis. TGF-β transduces its downstream signalling by phosphorylation of smad2/3 and also regulates epithelial-mesenchymal-transition (EMT), a program centrally involved in activation of fibroblasts. Renal fibrosis was induced in Swiss albino mice by unilateral ureteral obstruction of animals. Kidney tissues were evaluated for fibrotic protein expression by western blot and immunohistochemistry. The administration of nimbolide (NB) to UUO animals reduced the oxidative stress, expression of ECM proteins, TGF-β, p-smad and EMT program. Further, NB administration also improved histoarchitecture of obstructed kidney and reduced the collagen deposition in kidney. Our results provided compelling evidence to support antifibrotic activity of NB by reduction in oxidative stress, TGF-β, and EMT program in fibrotic kidney. The administration of NB in animals blunted the UUO-induced renal injury, inflammation and reduced fibrogenesis in obstructed kidney.

Association of Ambient Air Pollution with Increased Liver Enzymes in Korean Adults

An association between exposure to air pollution and liver enzymes in certain areas or older people has been reported in the literature; however, it cannot be generalized to the general population. We investigated the association between air pollution, liver enzyme levels, and alcohol consumption using nationwide data of South Korean adults. Air pollutants included particulate matter with an aerodynamic diameter ≤10 µm (PM₁₀), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and carbon monoxide (CO). Liver enzymes included alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Exposure to air pollutants were significantly associated with elevation of log ALT and log AST, especially increases from 0.0073 IU/L (95% confidence interval (CI) = 0.0042, 0.0104) to 0.0251 IU/L (95% CI = 0.0132, 0.0371) per interquartile range (IQR) increase of each pollutant (all pollutants: p < 0.001). Association of the liver enzymes with PM₁₀ (β (95% CI) = 0.0285 IU/L (0.0201, 0.0368) for log ALT; β (95% CI) = 0.0139 IU/L (0.0079, 0.0198) for log AST) and CO (β (95% CI) = 0.0247 IU/L (0.0182, 0.0311) for log ALT; β (95% CI) = 0.0164 IU/L (0.0118, 0.0210) for log AST) were only significant among drinkers. Our findings suggest that chronic exposure to PM₁₀ and CO is a risk factor for liver enzymes increases among the general adult population who admitted to drinking alcohol.

Antioxidant and hepatoprotective activities of modified polysaccharides from Coprinus comatus in mice with alcohol-induced liver injury

A modified polysaccharide named MPCC from Coprinus comatus (MPCC) was obtained by the snailase hydrolysis. And the hepatoprotective effects on alcohol-induced liver injury and preliminary structure features were investigated. For in vivo hepatoprotective abilities, MPCC significantly attenuated the hepatic and serum lipid levels, obviously enhanced antioxidant enzyme activities, markedly improved alcohol metabolism system and inflammatory response, and mitigated alcohol-induced liver injury histopathologically, providing references for the exploitation of MPCC as functional foods or natural drugs against the alcohol-induced liver injury. Additionally, MPCC containing fucose (Fuc), ribose (Rib), arabinose (Ara), xylose (Xyl), mannose (Man), galactose (Gal) and glucose (Glu) with the a α- and β-configuration in a percentage composition of 0.91%, 0.71%, 0.45%, 1.60%, 2.04%, 4.41% and 89.88% via gas chromatography (GC), Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) analysis.

Chemical induction of hepatic apoptosis in rodents

The urge of identifying new pharmacological interventions to prevent or attenuate liver injury is of critical importance and needs an expanded experimental toolbox. Hepatocyte injury and cellular death is a prominent feature behind the pathology of liver diseases. Several research activities focused on identifying chemicals and hepatotoxicants that induce cell death by apoptosis, in addition to presenting its corresponding signaling pathway. Although such efforts provided further understanding of the mechanisms of cell death, it has also raised confusion concerning identifying the involvement of several modes of cell death including apoptosis, necrosis and fibrosis. The current review highlights the ability of several chemicals and potential hepatotoxicants to induce liver damage in rodents by means of apoptosis while the probable involvement of other modes of cell death is also exposed. Thus, several chemical substances including hepatotoxins, mycotoxins, hyperglycemia inducers, metallic nanoparticles and immunosuppressant drugs are reviewed to explore the hepatic cytotoxic spectrum they could exert on hepatocytes of rodents. In addition, the current review address the mechanism by which hepatotoxicity is initiated in hepatocytes in different rodents aiding the researcher in choosing the right animal model for a better research outcome.

Lipid peroxidation derived reactive aldehydes in alcoholic liver disease

Lipid peroxidation is a known consequence of oxidative stress and is thought to play a key role in numerous disease pathologies, including alcoholic liver disease (ALD). The overaccumulation of lipid peroxidation products during chronic alcohol consumption results in pathogenic lesions on protein, DNA, and lipids throughout the cell. Molecular adducts due to secondary end products of lipid peroxidation impact a host of biochemical processes, including inflammation, antioxidant defense, and metabolism. The aggregate burden of lipid peroxidation which occurs due to chronic alcohol metabolism, including downstream signaling events, contributes to the development and progression of ALD. In this current opinion we highlight recent studies and approaches relating cellular mechanisms of lipid peroxidation to the pathogenesis of alcoholic liver disease.

Liver fibrosis: Pathophysiology, pathogenetic targets and clinical issues

The progression of chronic liver diseases (CLD), irrespective of etiology, involves chronic parenchymal injury, persistent activation of inflammatory response as well as sustained activation of liver fibrogenesis and wound healing response. Liver fibrogenesis, is a dynamic, highly integrated molecular, cellular and tissue process responsible for driving the excess accumulation of extracellular matrix (ECM) components (i.e., liver fibrosis) sustained by an eterogeneous population of hepatic myofibroblasts (MFs). The process of liver fibrogenesis recognizes a number of common and etiology-independent mechanisms and events but it is also significantly influenced by the specific etiology, as also reflected by peculiar morphological patterns of liver fibrosis development. In this review we will analyze the most relevant established and/or emerging pathophysiological issues underlying CLD progression with a focus on the role of critical hepatic cell populations, mechanisms and signaling pathways involved, as they represent potential therapeutic targets, to finally analyze selected and relevant clinical issues.

Recent advances in understanding liver fibrosis: bridging basic science and individualized treatment concepts

Hepatic fibrosis is characterized by the formation and deposition of excess fibrous connective tissue, leading to progressive architectural tissue remodeling. Irrespective of the underlying noxious trigger, tissue damage induces an inflammatory response involving the local vascular system and the immune system and a systemic mobilization of endocrine and neurological mediators, ultimately leading to the activation of matrix-producing cell populations. Genetic disorders, chronic viral infection, alcohol abuse, autoimmune attacks, metabolic disorders, cholestasis, alterations in bile acid composition or concentration, venous obstruction, and parasite infections are well-established factors that predispose one to hepatic fibrosis. In addition, excess fat and other lipotoxic mediators provoking endoplasmic reticulum stress, alteration of mitochondrial function, oxidative stress, and modifications in the microbiota are associated with non-alcoholic fatty liver disease and, subsequently, the initiation and progression of hepatic fibrosis. Multidisciplinary panels of experts have developed practice guidelines, including recommendations of preferred therapeutic approaches to a specific cause of hepatic disease, stage of fibrosis, or occurring co-morbidities associated with ongoing loss of hepatic function. Here, we summarize the factors leading to liver fibrosis and the current concepts in anti-fibrotic therapies.

Salvianolic acid A alleviates chronic ethanol-induced liver injury via promotion of β-catenin nuclear accumulation by restoring SIRT1 in rats

In recent years, alcoholic liver disease (ALD) has emerged as a growing public health problem worldwide. β-catenin plays an important role in the growth, development, regeneration and metabolic activity of the liver. Salvianolic acid A (SalA) is a water-soluble component from the root extract of Salvia miltiorrhiza Bunge, and its effect on ALD has not yet been investigated. This study aimed to investigate the effect of SalA on chronic alcohol-induced liver injury and to explore the role of SIRT1-mediated β-catenin deacetylation in such an effect. In this study, SalA treatment significantly alleviated the accumulation of lipid droplets and reduced the plasma alanine aminotransferase (ALT), aspartate aminotransferase (AST), total cholesterol (TC), triglyceride (TG), alcohol and ammonia levels in rats. SalA enhanced ethanol and ammonia metabolism and maintained mitochondrial homeostasis. Moreover, SalA restored the activity of the major ethanol-metabolizing enzymes and oxidative stress functions in the liver. Importantly, we found that SalA treatment effectively inhibited the ethanol-mediated decrease in nuclear β-catenin by upregulating SIRT1 in the liver. SIRT1 then deacetylated β-catenin to promote its accumulation in the nucleus, thereby preventing alcohol-induced liver injury. The results demonstrate that the SIRT1/β-catenin pathway is a key therapeutic target in liver injury caused by chronic alcohol exposure and that SalA protects against alcohol-induced liver injury via the SIRT1-mediated deacetylation of β-catenin.

Aldehyde dehydrogenase 2 gene polymorphisms and liver diseases

Liver diseases are one of major causes of disease burden in China. The composition of chronic liver diseases has changed significantly in China over the past years. The incidence of alcoholic liver disease has increased gradually. Acetaldehyde dehydrogenase 2 (ALDH2) is the principle enzyme responsible for hepatic metabolism of ethanol. Approximately 8% of individuals have the inactive ALDH2 genotype around the world, especially in the East Asian population. Presence of the mutant or inactive ALDH2*2 gene may lead to accumulation of acetaldehyde as the ethanol metabolite. Acetaldehyde is a toxic material which can cause multiple organs to be injured in the individuals with acetaldehyde accumulation. The relationship between the mutant ALDH2*2 gene and a variety of liver disorders including alcoholic liver disease needs to be explored. In the present article, we review the recent advances in understanding the relationship between ALDH2 gene polymorphisms and liver diseases, in order to provide a better understanding of the difference in the characteristics of liver disease between the Eastern and Western populations, which can help develop new strategies to prevent and treat liver diseases.

Pathophysiology of liver fibrosis and the methodological barriers to the development of anti-fibrogenic agents

Liver fibrosis and cirrhosis resulting from long-standing liver damage represents a major health care burden worldwide. To date, there is no anti-fibrogenic agent available, making liver transplantation the only curative treatment for decompensated cirrhotic liver disease. Liver fibrosis can result from different underlying chronic liver disease, such as chronic viral infection, excessive alcohol consumption, fatty liver disease or autoimmune liver diseases. It is becoming increasingly recognised that as a result from different pathogenic mechanisms liver fibrosis must be considered as many different diseases for which individual treatment strategies need to be developed. Moreover, the pathogenic changes of both liver architecture and vascularisation in cirrhotic livers, as well as the lack of "true-to-life" in vitro models have impeded the development of an effective anti-fibrogenic drug. Thus, in order to identify an efficient anti-fibrogenic compound, novel in-vitro models mimicking the interplay between pro-fibrogenic cell populations, immune cells and, importantly, the extracellular matrix need to be developed.

Quantification of skin erythema response to topical alcohol in alcohol-intolerant East Asians

BACKGROUND/PURPOSE

Severe alcohol intolerance characterized by flushing, headache, nausea, and tachycardia even after very modest oral alcohol consumption, is common among East Asians (Chinese, Japanese, Koreans) and has been associated with the accumulation of acetaldehyde resulting from genetic polymorphism of aldehyde dehydrogenase (ALDH). These individuals also display erythema of the skin in response to exposure to topical alcohol. We have recently observed that dietary phytochemicals such as sulforaphane can accelerate the disposal of acetaldehyde from cells and animals by inducing ALDH. The goal of this study was to quantify the erythema response of skin to topical alcohol exposure.

METHODS

The erythema response of the forearm skin of healthy Japanese with unusual alcohol sensitivity evoked by a range of very low doses of alcohol (2, 4, 8, and 16 μmol/cm² ) was determined by means of a chromometer, which measures a* values (red-green scale).

RESULTS

The magnitude of the a* response (∆a*) to alcohol was time- and dose-dependent, but differed considerably among individuals. It was much higher in those individuals who claimed to be alcohol intolerant, and ∆a* was unrelated to the initial a* values of the skin prior to alcohol challenge.

CONCLUSION

The ∆a* index is suitable for the quantitative determination of topical alcohol-induced erythema response, and the evaluation of effectiveness of protective strategies against erythema response.

Changes in human hepatic metabolism in steatosis and cirrhosis

AIM

To understand the underlying metabolic changes in human liver disease we have applied nuclear magnetic resonance (NMR) metabolomics analysis to human liver tissue.

METHODS

We have carried out pilot study using ¹H-NMR to derive metabolomic signatures from human liver from patients with steatosis, nonalcoholic steatohepatitis (NASH) or alcohol-related liver damage (ARLD) to identify species that can predict outcome and discriminate between alcohol and metabolic-induced liver injuries.

RESULTS

Changes in branched chain amino acid homeostasis, tricarboxylic acid cycle and purine biosynthesis intermediates along with betaine were associated with the development of cirrhosis in both ARLD and nonalcoholic fatty liver disease. Species such as propylene glycol and as yet unidentified moieties that allowed discrimination between NASH and ARLD samples were also detected using our approach.

CONCLUSION

Our high throughput, non-destructive technique for multiple analyte quantification in human liver specimens has potential for identification of biomarkers with prognostic and diagnostic significance.

The stellate cell system (vitamin A-storing cell system)

Past, present, and future research into hepatic stellate cells (HSCs, also called vitamin A-storing cells, lipocytes, interstitial cells, fat-storing cells, or Ito cells) are summarized and discussed in this review. Kupffer discovered black-stained cells in the liver using the gold chloride method and named them stellate cells (Sternzellen in German) in 1876. Wake rediscovered the cells in 1971 using the same gold chloride method and various modern histological techniques including electron microscopy. Between their discovery and rediscovery, HSCs disappeared from the research history. Their identification, the establishment of cell isolation and culture methods, and the development of cellular and molecular biological techniques promoted HSC research after their rediscovery. In mammals, HSCs exist in the space between liver parenchymal cells (PCs) or hepatocytes and liver sinusoidal endothelial cells (LSECs) of the hepatic lobule, and store 50-80% of all vitamin A in the body as retinyl ester in lipid droplets in the cytoplasm. SCs also exist in extrahepatic organs such as pancreas, lung, and kidney. Hepatic (HSCs) and extrahepatic stellate cells (EHSCs) form the stellate cell (SC) system or SC family; the main storage site of vitamin A in the body is HSCs in the liver. In pathological conditions such as liver fibrosis, HSCs lose vitamin A, and synthesize a large amount of extracellular matrix (ECM) components including collagen, proteoglycan, glycosaminoglycan, and adhesive glycoproteins. The morphology of these cells also changes from the star-shaped HSCs to that of fibroblasts or myofibroblasts.

New therapeutic targets in alcoholic hepatitis

Alcoholic liver disease (ALD) is a leading cause of liver-related morbidity and mortality worldwide. ALD encompasses a spectrum of disorders including asymptomatic steatosis, steatohepatitis, fibrosis, cirrhosis and its related complications, and the acute-on-chronic state of alcoholic hepatitis. While multidisciplinary efforts continue to be aimed at curbing progression of this spectrum of disorders, there is an urgent need to focus our efforts on effective therapeutic interventions for alcoholic hepatitis (AH), the most severe form of ALD. AH is characterized by an abrupt development of jaundice and complications related to liver insufficiency and portal hypertension in patients with heavy alcohol intake. The mortality of patients with severe AH is very high (20-50 % at 3 months). The current therapeutic regimens are limited. The development of new therapies requires translational studies in human samples and suitable animal models that reproduce clinical and histological features of human AH. This review article summarizes the clinical syndrome, pre-clinical translational tools, and pathogenesis of AH at a molecular and cellular level, with the aim of identifying new targets of potential therapeutic intervention.

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

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

New Mechanism of Hepatic Fibrogenesis: Hepatitis C Virus Infection Induces Transforming Growth Factor β1 Production through Glucose-Regulated Protein 94

Hepatitis C virus (HCV) is one of the leading causes of chronic liver inflammatory disease (hepatitis), which often leads to more severe diseases, such as liver fibrosis, cirrhosis, and hepatocellular carcinoma. Liver fibrosis, in particular, is a major pathogenic consequence of HCV infection, and transforming growth factor β1 (TGF-β1) plays a key role in its pathogenesis. Several HCV proteins have been suggested to either augment or suppress the expression of TGF-β1 by HCV-infected cells. Here, we report that TGF-β1 levels are elevated in HCV-infected hepatocytes cultured in vitro and in liver tissue of HCV patients. Notably, the level of TGF-β1 in media from in vitro-cultured HCV-infected hepatocytes was high enough to activate primary hepatic stellate cells isolated from rats. This indicates that TGF-β1 secreted by HCV-infected hepatocytes is likely to play a key role in the liver fibrosis observed in HCV patients. Moreover, we showed that HCV E2 protein triggers the production of TGF-β1 by HCV-infected cells through overproduction of glucose-regulated protein 94 (GRP94).

IMPORTANCE

Hepatic fibrosis is a critical step in liver cirrhosis caused by hepatitis C virus infection. It is already known that immune cells, including Kupffer cells, mediate liver fibrosis. Recently, several papers have suggested that HCV-infected hepatocytes also significantly produce TGF-β1. Here, we provide the first examination of TGF-β1 levels in the hepatocytes of HCV patients. Using an HCV culture system, we showed that HCV infection increases TGF-β1 production in hepatocytes. Furthermore, we confirmed that the amount of TGF-β1 secreted by HCV-infected hepatocytes was sufficient to activate primary hepatic stellate cells. To understand the molecular basis of TGF-β1 production in HCV-infected hepatocytes, we used HCV replicons and various stable cell lines. Finally, we elucidated that HCV E2 triggered TGF-β1 secretion via GRP94 mediated NF-κB activation. This study contributes to the understanding of liver fibrosis by HCV and suggests a new potential target (GRP94) for blocking liver cirrhosis in HCV patients.

Alcoholic Steatosis in Different Strains of Rat: A Comparative Study

Background

Different strains of rats have been used to study alcoholic liver disease (ALD) while the reason for selecting a particular rat strain was not apparent.

Purpose

The aim of our study was to compare outbred (Wistar) and inbred (Fischer) strains to evaluate pathological, biochemical changes, and gene expression differences associated with ethanol-induced early hepatic steatosis.

Study Design

Male Wistar and Fischer-344 rats were pair-fed for 6 weeks with or without 5% ethanol in Lieber-DeCarli liquid diet. Livers were analyzed for histological and lipid-related differences.

Results

Hepatic midzonal steatosis was mainly found in Wistar rats while Fischer rats showed mostly pericentral steatosis. Increased hepatic steatosis in ethanol-fed Wistar rats is supported by increases in lipids with related genes and transcription factors involved in fatty acid and triglyceride synthesis.

Conclusion

Our data showed that Fischer rats are relatively less prone to ethanol-mediated steatosis with pericentral lipid deposition pattern in the liver which is similar to humans and show no trace level of lipid accumulation in pair-fed controls as observed in Wistar (outbred) strain. Therefore, Fischer rats are better suited for lipid studies in an early development of ALD.

Dysregulation of skeletal muscle protein metabolism by alcohol

Alcohol abuse, either by acute intoxication or prolonged excessive consumption, leads to pathological changes in many organs and tissues including skeletal muscle. As muscle protein serves not only a contractile function but also as a metabolic reserve for amino acids, which are used to support the energy needs of other tissues, its content is tightly regulated and dynamic. This review focuses on the etiology by which alcohol perturbs skeletal muscle protein balance and thereby over time produces muscle wasting and weakness. The preponderance of data suggest that alcohol primarily impairs global protein synthesis, under basal conditions as well as in response to several anabolic stimuli including growth factors, nutrients, and muscle contraction. This inhibitory effect of alcohol is mediated, at least in part, by a reduction in mTOR kinase activity via a mechanism that remains poorly defined but likely involves altered protein-protein interactions within mTOR complex 1. Furthermore, alcohol can exacerbate the decrement in mTOR and/or muscle protein synthesis present in other catabolic states. In contrast, alcohol-induced changes in muscle protein degradation, either global or via specific modulation of the ubiquitin-proteasome or autophagy pathways, are relatively inconsistent and may be model dependent. Herein, changes produced by acute intoxication versus chronic ingestion are contrasted in relation to skeletal muscle metabolism, and limitations as well as opportunities for future research are discussed. As the proportion of more economically developed countries ages and chronic illness becomes more prevalent, a better understanding of the etiology of biomedical consequences of alcohol use disorders is warranted.

Primary biliary cirrhosis-associated hepatocellular carcinoma in Chinese patients: Incidence and risk factors

AIM: To investigate the incidence, characteristics, and risk factors for hepatocellular carcinoma (HCC) in Chinese patients with primary biliary cirrhosis (PBC).

METHODS: We reviewed the data of 52 PBC-associated HCC patients treated at Beijing 302 Hospital from January 2002 to December 2013 and analyzed its incidence and characteristics between the two genders. The risk factors for PBC-associated HCC were analyzed via a case-control study comprising 20 PBC patients with HCC and 77 matched controls without HCC. The matched factors included gender, age, follow-up period and Child-Pugh scores. Conditional logistic regression was used to evaluate the odds ratios of potential risk factors for HCC development. A P < 0.05 was considered statistically significant.

RESULTS: The incidence of HCC in Chinese PBC patients was 4.13% (52/1255) and was significantly higher in the males (9.52%) than in the females (3.31%). Among the 52 PBC patients with HCC, 55.76% (29/52) were diagnosed with HCC and PBC simultaneously, and 5.76% (3/52) were diagnosed with HCC before PBC. The males with PBC-associated HCC were more likely than the females to have undergone blood transfusion (18.75% vs 8.33%, P = 0.043), consumed alcohol (31.25% vs 8.33%, P = 0.010), smoked (31.25% vs 8.33%, P = 0.010), had a family history of malignancy (25% vs 5.56%, P = 0.012), and had serious liver inflammation, as indicated by the elevated levels of alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and γ-glutamyl transpeptidase (P < 0.05). Conditional logistic regression analysis revealed that body mass index (BMI) ≥ 25 [adjusted odds ratio (AOR) = 1.116, 95%CI: 1.002-1.244, P = 0.045] and history of alcohol intake (AOR = 10.294, 95%CI: 1.108-95.680, P = 0.040) were significantly associated with increased odds of HCC development in PBC patients.

CONCLUSION: HCC is not rare in Chinese PBC patients. Risk factors for PBC-associated HCC include BMI ≥ 25 and a history of alcohol intake. In addition to regular monitoring, PBC patients may benefit from abstinence from alcohol and body weight control.

Pathogenesis of alcoholic liver disease: Role of oxidative metabolism

Alcohol consumption is a predominant etiological factor in the pathogenesis of chronic liver diseases, resulting in fatty liver, alcoholic hepatitis, fibrosis/cirrhosis, and hepatocellular carcinoma (HCC). Although the pathogenesis of alcoholic liver disease (ALD) involves complex and still unclear biological processes, the oxidative metabolites of ethanol such as acetaldehyde and reactive oxygen species (ROS) play a preeminent role in the clinical and pathological spectrum of ALD. Ethanol oxidative metabolism influences intracellular signaling pathways and deranges the transcriptional control of several genes, leading to fat accumulation, fibrogenesis and activation of innate and adaptive immunity. Acetaldehyde is known to be toxic to the liver and alters lipid homeostasis, decreasing peroxisome proliferator-activated receptors and increasing sterol regulatory element binding protein activity via an AMP-activated protein kinase (AMPK)-dependent mechanism. AMPK activation by ROS modulates autophagy, which has an important role in removing lipid droplets. Acetaldehyde and aldehydes generated from lipid peroxidation induce collagen synthesis by their ability to form protein adducts that activate transforming-growth-factor-β-dependent and independent profibrogenic pathways in activated hepatic stellate cells (HSCs). Furthermore, activation of innate and adaptive immunity in response to ethanol metabolism plays a key role in the development and progression of ALD. Acetaldehyde alters the intestinal barrier and promote lipopolysaccharide (LPS) translocation by disrupting tight and adherent junctions in human colonic mucosa. Acetaldehyde and LPS induce Kupffer cells to release ROS and proinflammatory cytokines and chemokines that contribute to neutrophils infiltration. In addition, alcohol consumption inhibits natural killer cells that are cytotoxic to HSCs and thus have an important antifibrotic function in the liver. Ethanol metabolism may also interfere with cell-mediated adaptive immunity by impairing proteasome function in macrophages and dendritic cells, and consequently alters allogenic antigen presentation. Finally, acetaldehyde and ROS have a role in alcohol-related carcinogenesis because they can form DNA adducts that are prone to mutagenesis, and they interfere with methylation, synthesis and repair of DNA, thereby increasing HCC susceptibility.

Curcumol induces HSC-T6 cell death through suppression of Bcl-2: involvement of PI3K and NF-κB pathways

The major feature in the molecular pathogenesis of hepatic fibrosis requires maintenance of the activated hepatic stellate cells (HSCs) phenotype by both proliferation and inhibition of apoptosis. Thus, the induction of activated HSCs apoptosis has been proposed as an antifibrotic treatment strategy. Curcumol has pro-apoptotic activity in a number of cancer cell types. The aim of this study is to test the hypothesis that the interruption of the phosphatidylinositol 3 kinase (PI3K)/nuclear factor-κB (NF-κB) signaling pathway by curcumol might induce apoptosis of activated HSCs. Our results indicated that curcumol-induced growth inhibition correlated with apoptosis induction as evidenced by Annexin V staining, and cleavage of caspase-3 and poly (ADP-ribose) polymerase (PARP) in HSC-T6. Importantly, we show that the apoptotic effect of curcumol was specific to the activated HSCs (HSC-T6). Suppression of the NF-κB translocation via inhibition of IκB-α phosphorylation by the curcumol led to the inhibition of expression of NF-κB-regulated gene, e.g. Bcl-xL and Bcl-2, in a PI3K-dependent manner, which is upstream of NF-κB activation. Also, curcumol-mediated apoptosis of HSC-T6 were reversed by LY294002 and Bay 11-7082. Taken together, our findings perfectly support the hypothesis and demonstrate that the inhibition of PI3K/NF-κB pathway by curcumol lead to HSC-T6 apoptosis. Thus, our study indicates that curcumol is a potential candidate for further preclinical study aimed at the treatment of liver fibrosis.