Changes in the pathogenesis of alcohol-induced liver disease — Preclinical studies

Alpha-Asarone attenuates alcohol-induced hepatotoxicity in a murine model by ameliorating oxidative stress, inflammation, and modulating apoptotic-Autophagic cell death

Alcoholic liver disease (ALD) is a major cause of chronic liver injury characterized by steatosis, inflammation, and fibrosis. This study explored the hepatoprotective mechanisms of alpha-asarone in a mouse model of chronic-binge alcohol feeding. Adult male mice were randomized into control, alcohol, and alcohol plus alpha-asarone groups. Serum aminotransferases and histopathology assessed liver injury. Oxidative stress was evaluated via malondialdehyde content, glutathione, superoxide dismutase, and catalase activities. Pro-inflammatory cytokines TNF-α, IL-1β, and IL-6 were quantified by ELISA. P53-mediated apoptosis was determined by immunohistochemistry. Key autophagy markers phospho-AMPK, AMPK, Beclin-1, LC3-I/LC3-II ratio, and LC3 were examined by immunoblotting. Alcohol administration increased serum ALT, AST and ALP, indicating hepatocellular damage. This liver dysfunction was associated with increased oxidative stress, inflammation, p53 expression and altered autophagy. Alpha-asarone treatment significantly decreased ALT, AST and ALP levels and improved histological architecture versus alcohol alone. Alpha-asarone also mitigated oxidative stress, reduced TNF-α, IL-1β and IL-6 levels, ameliorated p53 overexpression and favorably modulated autophagy markers. Our findings demonstrate that alpha-asarone confers protective effects against ALD by enhancing antioxidant defenses, suppressing hepatic inflammation, regulating apoptotic signaling, and restoring autophagic flux. This preclinical study provides compelling evidence for the therapeutic potential of alpha-asarone in attenuating alcohol-induced liver injury and warrants further evaluation as a pharmacotherapy for ALD.

Protective effects of rare earth lanthanum on acute ethanol-induced oxidative stress in mice via Keap 1/Nrf2/p62 activation

With the widespread application of rare earth elements (REEs) in environment safety, food and medicine, they accumulate in the ecosystem and different human organs where REEs exert certain biological effects. Low dose REEs are proved to perform antioxidant effects, while high concentration can cause oxidative stress. However, scant information about rational doses and underlying mechanism of REEs as oxidants/antioxidants were illustrated. To elucidate these problems, here we performed a study that the ICR mice were received 0.1, 0.2, 1.0, 2.0 and 20.0 mg/kg lanthanum nitrate (La(NO₃)₃) by gavage for 30 days, and then were given 12 mL/kg ethanol once to undergo acute ethanol-induced oxidative stress. The antioxidant enzymes, antioxidants, peroxides and related proteins in Keap 1/Nrf2/p62 signaling pathway were measured. The results showed that La(NO₃)₃ inhibited hepatic morphological alternations by histopathological examination. Meanwhile, elevated superoxide dismutase (SOD) and glutathione (GSH), coupled with decreased alanine aminotransferase (ALT), aspartate aminotransferase (AST), malondialdehyde (MDA) and protein carbonyl (PC) were observed in serum and liver tissues of mice by enzyme-linked immunosorbent assay test. Furthermore, western blot analysis demonstrated that oxidative stress was alleviated due to enhanced NF-E2-related factor 2 (Nrf2) and phosphorylated p62 expressions as well as lower Kelch-like ECH-associated protein-1 (Keap 1), followed by the activation of heme oxygenase 1 (HO-1), NAD(P)H quinone oxidoreductase 1 (NQO-1) and glutamate cysteine ligase, catalytic (GCLC) proteins. Our findings clearly highlighted that La(NO₃)₃ could restore the redox homeostasis disrupted by ethanol through provoking Keap 1/Nrf2/p62 signaling pathway, and the optimal dosages were 1.0 and 2.0 mg/kg.

The structural characteristics, antioxidant and hepatoprotection activities of polysaccharides from Chimonanthus nitens Oliv. leaves

This work aimed to investigate the structural characteristics, antioxidant activities and hepatoprotection effect of Chimonanthus nitens Oliv. leaves polysaccharides (COP) on alcohol-induced oxidative damage in mice. Physical and chemical analysis showed that COP contained four monosaccharides including arabinose (Ara), mannose (Man), glucose (Glu) and galactose (Gal), with mass percentages of 26.6%, 5.1%, 32.2% and 36.0%, respectively, which was a heteropolysaccharide with both α- and β- configurations. In vivo experiments indicated that oral administration COP significantly reduced the levels of ALT, AST and MDA in serum, and significantly increased the activity of SOD and GSH-Px. Mice pretreated with COP had a higher superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity in liver and lower content of TNF-α, IL-6 and IL-1β in the liver and serum when compared with alcohol exposure. In addition, the liver histopathological changes induced by alcohol returned to normal in the COP pretreatment group. These results suggest that COP has a protective effect on acute liver injury induced by alcohol.

Sex Differences, Cocaine Use, and Liver Fibrosis Among African Americans in the Miami Adult Studies on HIV Cohort

Background: HIV infection disproportionally affects African Americans. Liver disease is a major cause of non-HIV morbidity and mortality in this population. Substance abuse accelerates HIV disease and may facilitate progression of liver disease. This study investigated the relationship between sex differences and cocaine use with liver injury, characterized as hepatic fibrosis. Materials and Methods: A cross-sectional study was conducted on 544 African Americans [369 people living with HIV (PLWH) and 175 HIV seronegative] from the Miami Adult Studies on HIV (MASH) cohort. Cocaine use was determined with a validated self-reported questionnaire and confirmed with urine screen. Fasting blood was used to estimate liver fibrosis using the noninvasive fibrosis-4 (FIB-4) index. Results: Men living with HIV had 1.79 times higher odds for liver fibrosis than women living with HIV (p = 0.038). African American women had higher CD4 count (p = 0.001) and lower HIV viral load (p = 0.011) compared to African American men. Fewer women (PLWH and HIV seronegative) smoked cigarettes (p = 0.002), and fewer had hazardous or harmful alcohol use (p < 0.001) than men. Women also had higher body mass index (kg/m²) (p < 0.001) compared to men. No significant association was noted among HIV seronegative participants for liver fibrosis by sex differences or cocaine use. Among African Americans living with HIV, cocaine users were 1.68 times more likely to have liver fibrosis than cocaine nonusers (p = 0.044). Conclusions: Sex differences and cocaine use appear to affect liver disease among African Americans living with HIV pointing to the importance of identifying at-risk individuals to improve outcomes of liver disease.

The Preventative Effects of Procyanidin on Binge Ethanol-Induced Lipid Accumulation and ROS Overproduction via the Promotion of Hepatic Autophagy

SCOPE

Autophagy plays an important role in alleviating alcoholic liver disease (ALD). In this study, it is discovered that a dimer procyanidin (DPC) significantly prevented ALD by promoting hepatic autophagy.

METHODS AND RESULTS

Both cell and animal disease models stimulated by excessive ethanol are employed to evaluate the protective actions of DPC. Specifically, in vitro, DPC significantly decreased intracellular lipid deposition, diminished reactive oxygen species (ROS) formation, and elevated the level of mitochondrial membrane potential. These beneficial effects can be remarkably blocked by 3-methyladenine, a potent autophagy inhibitor, suggesting the autophagy-dependent protective role of DPC. In vivo, DPC pretreatment can also significantly reduce lipid accumulation, ROS overproduction, and elevated GSH content in the liver. Similarly, these protective effects of DPC can be partially reversed by chloroquine, a lysosomal inhibitor used to block the late-stage autophagy flux. Moreover, the determinations of LC3 and p62 protein expressions, autophagic flux assessments, and transmission electron microscopy observation further demonstrate the pro-autophagic effect of DPC.

CONCLUSIONS

DPC may activate hepatic autophagy to eliminate lipid droplets and damaged mitochondria, thereby reducing hepatic lipid disposition and ROS overproduction. This study demonstrates that DPC is a protective reagent on ALD, providing a novel strategy of fighting ALD.

Mangiferin improves hepatic damage-associated molecular patterns, lipid metabolic disorder and mitochondrial dysfunction in alcohol hepatitis rats

This study was conducted to investigate the beneficial effects and possible mechanism of action of mangiferin (MF) in alcohol hepatitis (AH) rats. Building on our previous study, the damage-associated molecular patterns (DAMPs), lipid metabolic disorder and mitochondrial dysfunction were investigated. MF effectively regulated the abnormal liver function, the levels of alcohol, FFAs and metal elements in serum. More importantly, MF improved the expression levels of mRNA and protein of PPAR-γ, OPA-1, Cav-1, EB1, NF-κB p65, NLRP3, Cas-1 and IL-1β, and decreased the positive protein expression rates of HSP90, HMGB1, SYK, CCL20, C-CAS-3, C-PARP and STARD1. Additionally, MF decreased the levels of fumarate, cAMP, xanthurenic acid and d-glucurone-6,3-lactone, and increased the levels of hippuric acid and phenylacetylglycine, and then adjusted the changes of phenylalanine metabolism, TCA cycle and ascorbate and aldarate metabolic pathways. The above results suggested that MF can effectively prevent AH by modulating specific AH-associated genes, potential biomarkers and metabolic pathways in AH rats, etc.

Optimization of Ultrasonic-Microwave Assisted Extraction and Hepatoprotective Activities of Polysaccharides from Trametes orientalis

Ultrasonic-microwave assisted extraction (UMAE) of Trametes orientalis polysaccharides was optimized by response surface methodology. Hepatoprotective effects of a purified T. orientalis polysaccharide (TOP-2) were evaluated by alcohol-induced liver injury model mice. The optimal UMAE parameters were indicated as below: ratio of water to raw material 28 mL/g, microwave power 114 W, extraction time 11 min. The polysaccharides yield was 7.52 ± 0.12%, which was well consistent with the predicted value of 7.54%. Pre-treatment with TOP-2 effectively increased the liver index and spleen index in alcohol-treated mice. The elevated serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels of mice after alcohol exposure were inhibited by TOP-2 administration. The liver tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) levels have decreased significantly as a result of alcohol exposure, while pre-treatment with TOP-2 could mitigate these consequences. Furthermore, pre-treatment with TOP-2 could efficiently boost the superoxidase dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) activities, and observably constrain the malondialdehyde (MDA) level. The findings suggest that TOP-2 might be useful for alleviating the alcohol-induced hepatotoxicity via its antioxidant and anti-inflammatory potential.

Cannabidiol attenuates alcohol-induced liver steatosis, metabolic dysregulation, inflammation and neutrophil-mediated injury

Cannabidiol (CBD) is a non-psychoactive component of marijuana, which has anti-inflammatory effects. It has also been approved by FDA for various orphan diseases for exploratory trials. Herein, we investigated the effects of CBD on liver injury induced by chronic plus binge alcohol feeding in mice. CBD or vehicle was administered daily throughout the alcohol feeding study. At the conclusion of the feeding protocol, serums samples, livers or isolated neutrophils were utilized for molecular biology, biochemistry and pathology analysis. CBD significantly attenuated the alcohol feeding-induced serum transaminase elevations, hepatic inflammation (mRNA expressions of TNFα, MCP1, IL1β, MIP2 and E-Selectin, and neutrophil accumulation), oxidative/nitrative stress (lipid peroxidation, 3-nitrotyrosine formation, and expression of reactive oxygen species generating enzyme NOX2). CBD treatment also attenuated the respiratory burst of neutrophils isolated from chronic plus binge alcohol fed mice or from human blood, and decreased the alcohol-induced increased liver triglyceride and fat droplet accumulation. Furthermore, CBD improved alcohol-induced hepatic metabolic dysregulation and steatosis by restoring changes in hepatic mRNA or protein expression of ACC-1, FASN, PPARα, MCAD, ADIPOR-1, and mCPT-1. Thus, CBD may have therapeutic potential in the treatment of alcoholic liver diseases associated with inflammation, oxidative stress and steatosis, which deserves exploration in human trials.

5-HMF Attenuates Liver Fibrosis in CCl4-Plus-Alcohol-Induced Mice by Suppression of Oxidative Stress

The aim of this study was to investigate the effects of 5-hydroxymethyl-2-furfural (5-HMF) on liver fibrosis induced by carbon tetrachloride (CCl₄) and alcohol. Male ICR mice were treated with CCl₄ dissolved in olive oil (10% v/v, 2.5 μg/L) intraperitoneally (i.p.), and given at a dose of 2.5×10^-5 mg/kg B.W. twice a week for 7 wk. Concurrently, mice received drinking water with or without alcohol. The mice in treatment groups and positive control group were gavaged with 5-HMF (7.5, 15, and 30 mg/kg B.W.) or Huganpian (350 mg/kg B.W.) daily starting in the fourth week and lasting for 4 wk. The blood samples were analyzed for biochemical markers of hepatic injury and tissue samples were subjected for estimation of liver antioxidants and histopathological studies. The concentrations of HA (hyaluronic acid), LN (laminin), CIV (collagen type IV), and MDA (malondialdehyde), as well as the serum levels of ALT (alanine aminotransferase) and AST (aspartate aminotransferase) were markedly reduced by 5-HMF. On the other hand, enzymatic antioxidants SOD (superoxide dismutase), CAT (catalase) and GSH-Px (glutathione peroxidase) were markedly elevated in liver tissue treated with 5-HMF. Histopathological examination revealed that 5-HMF treatment noticeably prevented hepatocyte apoptosis, fatty degeneration and inflammatory cell infiltration on liver fibrosis induced by CCl₄ and alcohol. Hoechst 33258 staining also revealed hepatocyte apoptosis. 5-HMF could exert protective effects against liver injury and reduce liver fibrosis induced by CCl₄ and alcohol in mice.

Enhanced colorectal cancer metastases in the alcohol-injured liver

Metastatic liver disease is a major cause of mortality in colorectal cancer (CRC) patients. Alcohol consumption is a noted risk factor for secondary cancers yet the role of alcoholic liver disease (ALD) in colorectal liver metastases (CRLM) is not defined. This work evaluated tumor cell colonization in the alcoholic host liver using a novel preclinical model of human CRC liver metastases. Immunocompromised Rag1-deficient mice were fed either ethanol (E) or isocaloric control (C) diets for 4 weeks prior to intrasplenic injection of LS174T human CRC cells. ALD and CRLM were evaluated 3 or 5 weeks post-LS174T cell injection with continued C/E diet administration. ALD was confirmed by increased serum transaminases, hepatic steatosis and expression of cytochrome P4502E1, a major ethanol-metabolizing enzyme. Alcohol-mediated liver dysfunction was validated by impaired endocytosis of asialoorosomucoid and carcinoembryonic antigen (CEA), indicators of hepatocellular injury and progressive CRC disease, respectively. Strikingly, the rate and burden of CRLM was distinctly enhanced in alcoholic livers with metastases observed earlier and more severely in E-fed mice. Further, alcohol-related increases (1.5-3.0 fold) were observed in the expression of hepatic cytokines (TNF-α, IL-1 beta, IL-6, IL-10) and other factors noted to be involved in the colonization of CRC cells including ICAM-1, CCL-2, CCL-7, MMP-2, and MMP-9. Also, alcoholic liver injury was associated with altered hepatic localization as well as increased circulating levels of CEA released from CRC cells. Altogether, these findings indicate that the alcoholic liver provides a permissive environment for the establishment of CRLM, possibly through CEA-related inflammatory mechanisms.

ADAR1 Prevents Liver Injury from Inflammation and Suppresses Interferon Production in Hepatocytes

Adenosine deaminase acting on RNA 1 (ADAR1) is an essential protein for embryonic liver development. ADAR1 loss is embryonically lethal because of severe liver damage. Although ADAR1 is required in adult livers to prevent liver cell death, as demonstrated by liver-specific conditional knockout (Alb-ADAR1(KO)) mice, the mechanism remains elusive. We systematically analyzed Alb-ADAR1(KO) mice for liver damage. Differentiation genes and inflammatory pathways were examined in hepatic tissues from Alb-ADAR1(KO) and littermate controls. Inducible ADAR1 KO mice were used to validate regulatory effects of ADAR1 on inflammatory cytokines. We found that Alb-ADAR1(KO) mice showed dramatic growth retardation and high mortality because of severe structural and functional damage to the liver, which showed overwhelming inflammation, cell death, fibrosis, fatty change, and compensatory regeneration. Simultaneously, Alb-ADAR1(KO) showed altered expression of key differentiation genes and significantly higher levels of hepatic inflammatory cytokines, especially type I interferons, which was also verified by inducible ADAR1 knockdown in primary hepatocyte cultures. We conclude that ADAR1 is an essential molecule for maintaining adult liver homeostasis and, in turn, morphological and functional integrity. It inhibits the production of type I interferons and other inflammatory cytokines. Our findings may provide novel insight in the pathogenesis of liver diseases caused by excessive inflammatory responses, including autoimmune hepatitis.

Downregulation of the small GTPase SAR1A: a key event underlying alcohol-induced Golgi fragmentation in hepatocytes

The hepatic asialoglycoprotein receptor (ASGP-R) is posttranslationally modified in the Golgi en route to the plasma membrane, where it mediates clearance of desialylated serum glycoproteins. It is known that content of plasma membrane-associated ASGP-R is decreased after ethanol exposure, although the mechanisms remain elusive. Previously, we found that formation of compact Golgi requires dimerization of the largest Golgi matrix protein giantin. We hypothesize that ethanol-impaired giantin function may be related to altered trafficking of ASGP-R. Here we report that in HepG2 cells expressing alcohol dehydrogenase and hepatocytes of ethanol-fed rats, ethanol metabolism results in Golgi disorganization. This process is initiated by dysfunction of SAR1A GTPase followed by altered COPII vesicle formation and impaired Golgi delivery of the protein disulfide isomerase A3 (PDIA3), an enzyme that catalyzes giantin dimerization. Additionally, we show that SAR1A gene silencing in hepatocytes mimics the effect of ethanol: dedimerization of giantin, arresting PDIA3 in the endoplasmic reticulum (ER) and large-scale alterations in Golgi architecture. Ethanol-induced Golgi fission has no effect on ER-to-Golgi transportation of ASGP-R, however, it results in its deposition in cis-medial-, but not trans-Golgi. Thus, alcohol-induced deficiency in COPII vesicle formation predetermines Golgi fragmentation which, in turn, compromises the Golgi-to-plasma membrane transportation of ASGP-R.

Ameliorative effects of 5-hydroxymethyl-2-furfural (5-HMF) from Schisandra chinensis on alcoholic liver oxidative injury in mice

The aim of this paper is to evaluate the protective effect of 5-hydroxymethyl-2-furfural (5-HMF) on acute alcohol-induced liver oxidative injury in mice. 5-HMF, a maillard reaction product, was isolated from the fruits of Schisandra chinensis for animal experiments. Experimental ICR mice were pretreated with different doses of 5-HMF (7.5, 15, and 30 mg/kg) for seven days by gavage feeding. Biochemical markers and enzymatic antioxidants from serum and liver tissue were examined. Our results showed that the activities of ALT (alanine aminotransferase), AST (aspartate transaminase), TC (total cholesterol), TG (triglyceride), L-DLC (low density lipoprotein) in serum and the levels of MDA (malondialdehyde) in liver tissue, decreased significantly (p < 0.05) in the 5-HMF-treated group compared with the alcohol group. On the contrary, enzymatic antioxidants CAT (catalase), GSH-Px (glutathione peroxidase), and GSH SOD (superoxide dismutase) were markedly elevated in liver tissue treated with 5-HMF (p < 0.05). Furthermore, the hepatic levels of pro-inflammatory response marker tumor necrosis factor-alpha (TNF-α) and interleukin-1β (IL-1β) were significantly suppressed (p < 0.05). Histopathological examination revealed that 5-HMF (30 mg/kg) pretreatment noticeably prevented alcohol-induced hepatocyte apoptosis and fatty degeneration. It is suggested that the hepatoprotective effects exhibited by 5-HMF on alcohol-induced liver oxidative injury may be due to its potent antioxidant properties.

Platycodin D isolated from the aerial parts of Platycodon grandiflorum protects alcohol-induced liver injury in mice

Platycodin D (PD) is the main active saponin of Platycodon grandiflorum (PG) and is reported to exhibit multiple biological effects, including anti-tumor, anti-inflammation, and anti-obesity properties.

Alcoholic and non-alcoholic steatohepatitis

This paper is based upon the "Charles Lieber Satellite Symposia" organized by Manuela G. Neuman at the Research Society on Alcoholism (RSA) Annual Meetings, 2013 and 2014. The present review includes pre-clinical, translational and clinical research that characterize alcoholic liver disease (ALD) and non-alcoholic steatohepatitis (NASH). In addition, a literature search in the discussed area was performed. Strong clinical and experimental evidence lead to recognition of the key toxic role of alcohol in the pathogenesis of ALD. The liver biopsy can confirm the etiology of NASH or alcoholic steatohepatitis (ASH) and assess structural alterations of cells, their organelles, as well as inflammatory activity. Three histological stages of ALD are simple steatosis, ASH, and chronic hepatitis with hepatic fibrosis or cirrhosis. These latter stages may also be associated with a number of cellular and histological changes, including the presence of Mallory's hyaline, megamitochondria, or perivenular and perisinusoidal fibrosis. Genetic polymorphisms of ethanol metabolizing enzymes such as cytochrome p450 (CYP) 2E1 activation may change the severity of ASH and NASH. Alcohol mediated hepatocarcinogenesis, immune response to alcohol in ASH, as well as the role of other risk factors such as its co-morbidities with chronic viral hepatitis in the presence or absence of human immunodeficiency virus are discussed. Dysregulation of hepatic methylation, as result of ethanol exposure, in hepatocytes transfected with hepatitis C virus (HCV), illustrates an impaired interferon signaling. The hepatotoxic effects of ethanol undermine the contribution of malnutrition to the liver injury. Dietary interventions such as micro and macronutrients, as well as changes to the microbiota are suggested. The clinical aspects of NASH, as part of metabolic syndrome in the aging population, are offered. The integrative symposia investigate different aspects of alcohol-induced liver damage and possible repair. We aim to (1) determine the immuno-pathology of alcohol-induced liver damage, (2) examine the role of genetics in the development of ASH, (3) propose diagnostic markers of ASH and NASH, (4) examine age differences, (5) develop common research tools to study alcohol-induced effects in clinical and pre-clinical studies, and (6) focus on factors that aggravate severity of organ-damage. The intention of these symposia is to advance the international profile of the biological research on alcoholism. We also wish to further our mission of leading the forum to progress the science and practice of translational research in alcoholism.

Toll-like receptor-mediated signaling cascade as a regulator of the inflammation network during alcoholic liver disease

Chronic abuse of alcohol leads to various histological abnormalities in the liver. These are conditions collectively known as alcoholic liver disease (ALD). Currently, ALD is considered to be one of the major causes of death worldwide. An impaired intestinal barrier with related endotoxemia is among the various pathogenetic factors. This is mainly characterized by circulating levels of lipopolysaccharide (LPS), considered critical for the onset of intra-hepatic inflammation. This in turn promotes hepatocellular damage and fibrosis in ALD. Elevated levels of LPS exert their effects by binding to Toll-like receptors (TLRs) which are expressed by all liver-resident cells. The activation of TLR signaling triggers an overproduction and release of some cytokines, which promote an autocatalytic cascade of other pro-inflammatory signals. In this review, we provide an overview of the mechanisms that sustain LPS-mediated activation of TLR signaling, reporting current experimental and clinical evidence of its role during inflammation in ALD.