Pathogenesis of alcoholic liver disease: the role of nuclear receptors

Aqueous extract of Laurus nobilis leaf accelerates the alcohol metabolism and prevents liver damage in single-ethanol binge rats

BACKGROUND/OBJECTIVES

Excessive alcohol consumption has harmful health effects, including alcohol hangovers and alcohol-related liver disease. Therefore, methods to accelerate the alcohol metabolism are needed. Laurus nobilis is a spice, flavoring agent, and traditional herbal medicine against various diseases. This study examined whether the standardized aqueous extract of L. nobilis leaves (LN) accelerates the alcohol metabolism and protects against liver damage in single-ethanol binge Sprague-Dawley (SD) rats.

MATERIALS/METHODS

LN was administered orally to SD rats 1 h before ethanol administration (3 g/kg body weight [BW]) at 100 and 300 mg/kg BW. Blood samples were collected 0.5, 1, 2, and 4 h after ethanol administration. The livers were excised 1 h after ethanol administration to determine the hepatic enzyme activity. The alcohol dehydrogenase (ADH), aldehyde dehydrogenase (ALDH), superoxide dismutase (SOD), and glutathione peroxidase (GPx) activities in the liver tissue were measured.

RESULTS

LN decreased the serum ethanol and acetaldehyde levels in ethanol-administered rats. LN increased the hepatic ADH and ALDH activities but decreased the alanine aminotransferase, aspartate aminotransferase, and gamma-glutamyl transferase activities in the ethanol-administered rats. In addition, LN inhibited lipid peroxidation and increased the activities of SOD and GPx.

CONCLUSIONS

LN modulates the mediators of various etiological effects of excessive alcohol consumption and enhances the alcohol metabolism and antioxidant activity, making it a potential candidate for hangover treatments.

The environmental pollutant, polychlorinated biphenyl 126, alters liver function in a rodent model of alcohol-associated liver disease

BACKGROUND

The prevalence of alcohol-associated liver disease (ALD), a subtype of fatty liver disease (FLD), continues to rise. ALD is a major cause of preventable death. Polychlorinated biphenyl (PCB) 126 is an environmentally relevant, dioxin-like pollutant whose negative metabolic effects have been well documented. In human and animal studies, PCB has been associated with the severity of nonalcoholic fatty liver disease (NAFLD). However, few studies have investigated whether exposures to environmental toxicants can worsen ALD. Thus, the objective of the current study was to develop an alcohol-plus-toxicant model to study how an environmental pollutant, PCB 126, impacts rodent ALD pathology.

METHODS

Briefly, male C57BL/6J mice were exposed to 0.2 mg/kg PCB 126 or corn oil vehicle four days prior to ethanol feeding using the chronic-binge (10-plus-one) model.

RESULTS

Concentrations of macromolecules, including hepatic lipids, carbohydrates, and protein (albumin) were impacted. Exposure to PCB 126 exacerbated hepatic steatosis and hepatomegaly in mice exposed to the chemical and fed an ethanol diet. Gene expression and the analysis of blood chemistry showed a potential net increase and retention of hepatic lipids and reductions in lipid oxidation and clearance capabilities. Depletion of glycogen and glucose was evident, which contributes to disease progression by generating systemic malnutrition. Granulocytic immune infiltrates were present but driven solely by ethanol feeding. Hepatic albumin gene expression and plasma levels were decreased by ~50% indicating a potential compromise of liver function. Finally, gene expression analyses indicated that the aryl hydrocarbon receptor and constitutive androstane receptor were activated by PCB 126 and ethanol, respectively.

CONCLUSIONS

Various environmental toxicants are known to modify or enhance FLD in high-fat diet models. Findings from the present study suggest that they interact with other lifestyle factors such as alcohol consumption to reprogram intermediary metabolism resulting in exacerbated ethanol-associated systemic malnutrition in ALD.

Similarities and Differences: A Comparative Review of the Molecular Mechanisms and Effectors of NAFLD and AFLD

Non-alcoholic fatty liver disease (NAFLD) and alcoholic fatty liver disease (AFLD) are the most prevalent metabolic liver diseases globally. Due to the complex pathogenic mechanisms of NAFLD and AFLD, no specific drugs were approved at present. Lipid accumulation, oxidative stress, insulin resistance, inflammation, and dietary habits are all closely related to the pathogenesis of NAFLD and AFLD. However, the mechanism that promotes disease progression has not been fully elucidated. Meanwhile, the gut microbiota and their metabolites also play an important role in the pathogenesis and development of NAFLD and AFLD. This article comparatively reviewed the shared and specific signaling pathways, clinical trials, and potential intervention effectors of NAFLD and AFLD, revealing their similarities and differences. By comparing the shared and specific molecular regulatory mechanisms, this paper provides mutual reference strategies for preventing and treating NAFLD, AFLD, and related metabolic diseases. Furthermore, it provides enlightenment for discovering novel therapies of safe and effective drugs targeting the metabolic liver disease.

Associations of persistent organic pollutants in human adipose tissue with retinoid levels and their relevance to the redox microenvironment

Humans are exposed to a myriad of chemical substances in both occupational and environmental settings. Persistent organic pollutants (POPs) have drawn attention for their adverse effects including cancer and endocrine disruption. Herein, the objectives were 1) to describe serum and adipose tissue retinol levels, along with serum retinol binding protein 4 (RBP4) concentrations, and 2) to assess the associations of adipose tissue POP levels with these retinoid parameters, as well as their potential interaction with the previously-observed POP-related disruption of redox microenvironment. Retinol was measured in both serum and adipose tissue along with RBP4 levels in serum samples of 236 participants of the GraMo adult cohort. Associations were explored by multivariable linear regression analyses and Weighted Quantile Sum regression. Polychlorinated biphenyls (PCBs) 180, 153 and 138 were related to decreased adipose tissue retinol levels and increased serum RBP4/retinol ratio. Dicofol concentrations > limit of detection were associated with decreased retinol levels in serum and adipose tissue. Additionally, increased adipose tissue retinol levels were linked to an attenuation in previously-reported associations of adipose tissue PCB-153 with in situ superoxide dismutase activity. Our results revealed a suggestive link between retinoids, PCBs and redox microenvironment, potentially relevant for both mechanistic and public health purposes.

Development and validation of radiomics model built by incorporating machine learning for identifying liver fibrosis and early-stage cirrhosis

BACKGROUND

Liver fibrosis (LF) continues to develop and eventually progresses to cirrhosis. However, LF and early-stage cirrhosis (ESC) can be reversed in some cases, while advanced cirrhosis is almost impossible to cure. Advances in quantitative imaging techniques have made it possible to replace the gold standard biopsy method with non-invasive imaging, such as radiomics. Therefore, the purpose of this study is to develop a radiomics model to identify LF and ESC.

METHODS

Patients with LF (n = 108) and ESC (n = 116) were enrolled in this study. As a control, patients with healthy livers were involved in the study (n = 145). Diffusion-weighted imaging (DWI) data sets with three b-values (0, 400, and 800 s/mm) of enrolled cases were collected in this study. Then, radiomics features were extracted from manually delineated volumes of interest. Two modeling strategies were performed after univariate analysis and feature selection. Finally, an optimal model was determined by the receiver operating characteristic area under the curve (AUC).

RESULTS

The optimal models were built in plan 1. For model 1 in plan 1, the AUCs of the training and validation cohorts were 0.973 (95% confidence interval [CI] 0.946-1.000) and 0.948 (95% CI 0.903-0.993), respectively. For model 2 in plan 1, the AUCs of the training and validation cohorts were 0.944, 95% CI 0.905 to 0.983, and 0.968, 95% CI 0.940 to 0.996, respectively.

CONCLUSIONS

Radiomics analysis of DWI images allows for accurate identification of LF and ESC, and the non-invasive biomarkers extracted from the functional DWI images can serve as a better alternative to biopsy.

Critical review on the use and abuse of alcohol. When the dose makes the difference

Nowadays harmful alcohol consumption represents one of the most important risk factors for the development of several type of chronic and acute diseases in the western countries, contributing to a great number of deaths. Focusing the attention on cancer development and progression, the scientific community has a large consensus in declaring the existence of a harmful association between alcohol consumption and liver, breast, upper aerodigestive tract (mouth, oropharynx, hypopharynx, and esophagus), pancreas and colon cancer appearance. However the precise biological links by which the alcohol could be responsible for cancer initiation and progression are not fully understood yet, even if the International Agency for Research on Cancer (IARC) indicated both ethanol and acetaldehyde as carcinogen for humans. The possible explanation of the effect exerted by ethanol and acetaldehyde could be related to direct genotoxicity, hormonal disturbance, triggering of oxidative stress and inflammation. In this review, we examine the relationship between alcohol dosage and associated diseases, with focus on alcohol-related cancers. Furthermore, to understand the potential molecular mechanisms of these diseases, the results of in vivo experiments on animal models were discussed.

Inhibitors of cellular stress overcome acute effects of ethanol on hippocampal plasticity and learning

Ethanol intoxication can produce marked changes in cognitive function including states in which the ability to learn and remember new information is completely disrupted. These defects likely reflect changes in the synaptic plasticity thought to underlie memory formation. We have studied mechanisms contributing to the adverse effects of ethanol on hippocampal long-term potentiation (LTP) and provided evidence that ethanol-mediated LTP inhibition involves a form of metaplasticity resulting from local metabolism of ethanol to acetaldehyde and untimely activation of N-methyl-d-aspartate receptors (NMDARs), both of which are neuronal stressors. In the present studies, we sought to understand the role of cellular stress in LTP defects, and demonstrate that ethanol's effects on LTP in the CA1 hippocampal region are overcome by agents that inhibit cellular stress responses, including ISRIB, a specific inhibitor of integrated stress responses, and GW3965, an agonist that acts at liver X receptors (LXRs) and dampens cellular stress. The agents that alter LTP inhibition also prevent the adverse effects of acute ethanol on one trial inhibitory avoidance learning. Unexpectedly, we found that the LXR agonist but not ISRIB overcomes effects of ethanol on synaptic responses mediated by N-methyl-d-aspartate receptors (NMDARs). These results have implications for understanding the adverse effects of ethanol and possibly for identifying novel paths to treatments that can prevent or overcome ethanol-induced cognitive dysfunction.

Clinical periodontal and dental findings in liver transplant patients: a systematic review and meta-analysis

Objectives This systematic review aimed to investigate the oral health of post-liver transplant recipients (postLTx), in terms of dental and periodontal clinical results.Data sources Pubmed/MEDLINE and Cochrane Library databases were searched electronically.Data selection Prospective, cross-sectional and case-control studies comparing periodontal and dental health of postLTx patients with healthy and/or pre-liver transplant patients.Data extraction This was performed independently by two authors. Quality assessment was done by using tools from the National Heart, Lung, and Blood Institute.Data synthesis Nine studies were eligible for inclusion in the systematic review. A meta-analysis was performed on gingival inflammation, expressed by scores, on four studies including healthy controls. The gingival index scores were significantly higher in postLTx patients compared with healthy controls (p <0.001). The weighted mean difference was 0.91 (95% confidence interval, 0.44 to 1.38, heterogeneity I² = 99.5%). Increased tendency of gingival enlargement was noticed in postLTx patients, especially after immunosuppression with Cyclosporine A. Controversial results were reported for the prevalence of caries in postLTx recipients, but there seems to be an increase.Conclusion The results suggest that patients with liver transplants, due to systemic condition and immunosuppressive therapy, exhibit a higher degree of gingival inflammation compared with unexposed patients.Prospero registration number: CRD42019121893.

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

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

Pedro Ximenez sun-dried grape must: a dietary supplement for a healthy longevity

Sun-dried Pedro Ximénez white grapes must (PXM) is a potent antioxidant that regularizes apoptosis, proliferation, and regeneration of the structure and the function of aged mice liver. PXM consumption contributes to a healthy aging process.

Investigating RNA expression profiles altered by nicotinamide mononucleotide therapy in a chronic model of alcoholic liver disease

BACKGROUND

Chronic alcohol consumption is a significant cause of liver disease worldwide. Several biochemical mechanisms have been linked to the initiation and progression of alcoholic liver disease (ALD) such as oxidative stress, inflammation, and metabolic dysregulation, including the disruption of NAD⁺/NADH. Indeed, an ethanol-mediated reduction in hepatic NAD⁺ levels is thought to be one factor underlying ethanol-induced steatosis, oxidative stress, steatohepatitis, insulin resistance, and inhibition of gluconeogenesis. Therefore, we applied a NAD⁺ boosting supplement to investigate alterations in the pathogenesis of early-stage ALD.

METHODS

To examine the impact of NAD⁺ therapy on the early stages of ALD, we utilized nicotinamide mononucleotide (NMN) at 500 mg/kg intraperitoneal injection every other day, for the duration of a Lieber-DeCarli 6-week chronic ethanol model in mice. Numerous strategies were employed to characterize the effect of NMN therapy, including the integration of RNA-seq, immunoblotting, and metabolomics analysis.

RESULTS

Our findings reveal that NMN therapy increased hepatic NAD⁺ levels, prevented an ethanol-induced increase in plasma ALT and AST, and changed the expression of 25% of the genes that were modulated by ethanol metabolism. These genes were associated with a number of pathways including the MAPK pathway. Interestingly, our analysis revealed that NMN treatment normalized Erk1/2 signaling and prevented an induction of Atf3 overexpression.

CONCLUSIONS

These findings reveal previously unreported mechanisms by which NMN supplementation alters hepatic gene expression and protein pathways to impact ethanol hepatotoxicity in an early-stage murine model of ALD. Overall, our data suggest further research is needed to fully characterize treatment paradigms and biochemical implications of NAD⁺-based interventions.

Hepatoprotective effects of Lactococcus chungangensis CAU 1447 in alcoholic liver disease

Alcoholic liver disease (ALD) is correlated with alcohol consumption, and ALD progression depends on various factors. Some lactic acid bacteria (LAB) are beneficial for mitigating ALD. However, the valuable effects of LAB-derived dairy products remain unclear. Here, we evaluated the effects of Lactococcus chungangensis CAU 1447 dry cells (CAU 1447) and cream cheese derived from CAU 1447 on ALD progression following long-term alcohol consumption in rats. Oral administration of CAU 1447 and CAU 1447 cream cheese significantly reduced alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, and triglyceride levels. We found that CAU 1447 and CAU 1447 cream cheese downregulated mRNA encoding various cytokines and antioxidative factors in the liver. Oral CAU 1447 cream cheese administration increased short-chain fatty acid, butyrate, and acetate levels in feces. Thus, administration of CAU 1447 and CAU 1447 cream cheese induced hepatoprotective effects, indicating potential applications as a supplement for ALD mitigation.

Role of the pregnane X receptor in binge ethanol-induced steatosis and hepatotoxicity

The pregnane X receptor (PXR, NR1I2) is a xenobiotic-sensing nuclear receptor that defends against toxic agents. We have shown that PXR promotes chronic ethanol (EtOH)-induced steatosis. Therefore, we examined the role of PXR in binge EtOH-induced hepatotoxicity. Male wild type (WT) and Pxr-null mice were orally administered three binge doses of EtOH (4.5 g/kg, every 12 hours) and euthanized four hours after the final dose. Pxr-null mice displayed higher basal mRNA levels of hepatic lipogenic transcription factor sterol regulatory element binding protein 1c (Srebp-1c) and its target stearoyl-CoA desaturase 1 (Scd1) and the lipid peroxide detoxifying aldo-keto reductase 1b7 (Akr1b7) and higher protein levels of EtOH-metabolizing alcohol dehydrogenase 1 (ADH1). In both genotypes, binge EtOH-induced triglyceride accumulation was associated with inhibition of fatty acid β-oxidation and upregulation of Srebp-1c- regulated lipogenic genes and hepatic CYP2E1 protein. Unexpectedly, gene expression of Cyp2b10, a constitutive androstane receptor target gene, implicated in EtOH hepatotoxicity, was PXR-dependent upregulated by binge EtOH. Also, PXR-dependent was the binge EtOH-induced inhibition of hepatic Akr1b8 mRNA, and protein levels of aldehyde dehydrogenase (ALDH) 1A1 and anti-apoptotic Bcl-2, but increased pro-apoptotic Bax protein expression, leading to increases in residual EtOH concentration and the cellular oxidative stress marker, malondialdehyde. In contrast, Pxr-null mice displayed increased Akr1b7 gene and ADH1 protein expression and hypertriglyceridemia following binge EtOH exposure. Taken together, this study demonstrates that PXR ablation prevents EtOH induced upregulation of Cyp2b10 and that PXR potentiates binge EtOH-induced oxidative stress and inhibition of EtOH catabolism, but protects against alcoholic hyperlipidemia.

Association between expression of nuclear receptor co-activator 5 protein and prognosis in postoperative patients with osteosarcoma

The aim of the present study was to investigate the association between the expression of nuclear receptor co-activator 5 protein (NCOA5) and the prognosis of postoperative patients with osteosarcoma. Human osteosarcoma samples were collected from 145 patients and normal bone tissues were collected from 100 individuals as controls. Immunohistochemistry (IHC) and reverse transcription-polymerase chain reaction (RT-PCR) were employed to measure the levels of NCOA5 protein in cases of human osteosarcoma. The results from the RT-PCR analysis demonstrated that the positive rate of NCOA5 mRNA expression in human osteosarcoma was 17.24% (25/145). The positive rate in normal bone tissues was 84.00% (84/100), which was significantly higher compared with that of human osteosarcoma tissues (χ²=33.166; P<0.001). IHC staining indicated that the positive rate of NCOA5 protein in the osteosarcoma samples was 26.21% (38/145). The positive rate in normal bone tissues was 82.00% (82/100), which was significantly increased compared with that of human osteosarcoma tissues (χ²=28.166; P<0.001). NCOA5 mRNA and protein expression levels were consistent in human osteosarcoma tissues, and were lower than in control tissues. The expression of NCOA5 was low in human osteosarcoma tissues, while it was high in normal bone tissues. These low NCOA5 expression levels were associated with postoperative survival of human osteosarcoma.

Pregnane X receptor promotes ethanol-induced hepatosteatosis in mice

The pregnane X receptor (PXR, NR1I2) is a xenobiotic-sensing nuclear receptor that modulates the metabolic response to drugs and toxic agents. Both PXR activation and deficiency promote hepatic triglyceride accumulation, a hallmark feature of alcoholic liver disease. However, the molecular mechanism of PXR-mediated activation of ethanol (EtOH)-induced steatosis is unclear. Here, using male wildtype (WT) and Pxr-null mice, we examined PXR-mediated regulation of chronic EtOH-induced hepatic lipid accumulation and hepatotoxicity. EtOH ingestion for 8 weeks significantly (1.8-fold) up-regulated Pxr mRNA levels in WT mice. The EtOH exposure also increased mRNAs encoding hepatic constitutive androstane receptor (3-fold) and its target, Cyp2b10 (220-fold), in a PXR-dependent manner. Furthermore, WT mice had higher serum EtOH levels and developed hepatic steatosis characterized by micro- and macrovesicular lipid accumulation. Consistent with the development of steatosis, lipogenic gene induction was significantly increased in WT mice, including sterol regulatory element-binding protein 1c target gene fatty-acid synthase (3.0-fold), early growth response-1 (3.2-fold), and TNFα (3.0-fold), whereas the expression of peroxisome proliferator-activated receptor α target genes was suppressed. Of note, PXR deficiency suppressed these changes and steatosis. Protein levels, but not mRNAs levels, of EtOH-metabolizing enzymes, including alcohol dehydrogenase 1, aldehyde dehydrogenase 1A1, and catalase, as well as the microsomal triglyceride transfer protein, involved in regulating lipid output were higher in Pxr-null than in WT mice. These findings establish that PXR signaling contributes to ALD development and suggest that PXR antagonists may provide a new approach for ALD therapy.

Therapeutic opportunities for alcoholic steatohepatitis and nonalcoholic steatohepatitis: exploiting similarities and differences in pathogenesis

Alcoholic steatohepatitis (ASH) and nonalcoholic steatohepatitis (NASH) are among the most frequent causes of chronic liver disease in the United States. Although the two entities are triggered by different etiologies - chronic alcohol consumption (ASH) and obesity-associated lipotoxicity (NASH) - they share overlapping histological and clinical features owing to common pathogenic mechanisms. These pathogenic processes include altered hepatocyte lipid metabolism, organelle dysfunction (i.e., ER stress), hepatocyte apoptosis, innate immune system activation, and hepatic stellate cell activation. Nonetheless, there are several disease-specific molecular signaling pathways, such as differential pathway activation downstream of TLR4 (MyD88-dependence in NASH versus MyD88-independence in ASH), inflammasome activation and IL-1β signaling in ASH, insulin resistance and lipotoxicity in NASH, and dysregulation of different microRNAs, which clearly highlight that ASH and NASH are two distinct biological entities. Both pathogenic similarities and differences have therapeutic implications. In this Review, we discuss these pathogenic mechanisms and their therapeutic implications for each disease, focusing on both shared and distinct targets.

Alcohol and Cancer: Mechanisms and Therapies

Several scientific and clinical studies have shown an association between chronic alcohol consumption and the occurrence of cancer in humans. The mechanism for alcohol-induced carcinogenesis has not been fully understood, although plausible events include genotoxic effects of acetaldehyde, cytochrome P450 2E1 (CYP2E1)-mediated generation of reactive oxygen species, aberrant metabolism of folate and retinoids, increased estrogen, and genetic polymorphisms. Here, we summarize the impact of alcohol drinking on the risk of cancer development and potential underlying molecular mechanisms. The interactions between alcohol abuse, anti-tumor immune response, tumor growth, and metastasis are complex. However, multiple studies have linked the immunosuppressive effects of alcohol with tumor progression and metastasis. The influence of alcohol on the host immune system and the development of possible effective immunotherapy for cancer in alcoholics are also discussed here. The conclusive biological effects of alcohol on tumor progression and malignancy have not been investigated extensively using an animal model that mimics the human disease. This review provides insights into cancer pathogenesis in alcoholics, alcohol and immune interactions in different cancers, and scope and future of targeted immunotherapeutic modalities in patients with alcohol abuse.

Alcohol extract of North American ginseng (Panax quinquefolius) reduces fatty liver, dyslipidemia, and other complications of metabolic syndrome in a mouse model

We investigated whether North American ginseng (Panax quinquefolius) could reduce development of the metabolic syndrome phenotype in a mouse model (ETKO) of the disease. Young ETKO mice have no disease but similar to humans start to develop the fatty liver, hypertriglyceridemia, obesity, and insulin resistance at 25-30 weeks of age, and the disease continues to progress with ageing. ETKO mice were orally given an ethanol extract of ginseng roots at 4 and 32 weeks of age. Treatments with ginseng eliminated the ETKO fatty liver, reduced hepatic and intestinal lipoprotein secretion, and reduced the level of circulating lipids. Improvements by ginseng treatments were manifested as a reduction in the expression of genes involved in the regulation of fatty acid and triglyceride (fat) synthesis and secretion by the lipoproteins on one hand, and the stimulation of fatty acid oxidation and triglyceride degradation by lipolysis on the other hand. These processes altogether improved glucose, fatty acid, and triglyceride metabolism, reduced liver fat load, and reversed the progression of metabolic syndrome. These data confirm that treatments with North American ginseng could alleviate metabolic syndrome through the maintenance of a better balance between glucose and fatty acid metabolism, lipoprotein secretion, and energy homeostasis in disease-prone states.

Dihydromyricetin modulates p62 and autophagy crosstalk with the Keap-1/Nrf2 pathway to alleviate ethanol-induced hepatic injury

Increasing evidence has demonstrated that dihydromyricetin (DMY) contains highly effective antioxidative, anti-inflammatory, anti-microbial and anti-diabetic properties. Nevertheless, the underlying hepatoprotective mechanisms of DMY have infrequently been reported thus far. In the present study, C57BL/6 mice were fed with the Lieber-DeCarli diet containing alcohol or isocaloric maltose dextrin as a control diet with or without DMY (75 and 150mg/kg/d bw) for 6 weeks. DMY significantly attenuated hepatic enzyme release, hepatic lipid peroxidation and triglyceride deposition induced by chronic alcohol exposure. In addition, DMY dramatically attenuated the alcohol-triggered elevation of the level of inflammatory cytokines and partially recovered hepatic pathological changes. Notably, DMY remarkably modified aberrant expression of CYP2E1, Keap-1 and HO-1 in the liver and simultaneously ameliorated disordered nuclear localization of NF-κB and Nrf2 to exert its hepatoprotective effects. Further mechanistic exploration suggested that DMY activated Nrf2, possibly mediated through the autophagy pathway. Analysis of the crosstalk among p62, Keap-1 and Nrf2 demonstrated that the p62 upregulation caused by DMY contributes to a positive feedback loop in Nrf2 activation. In summary, DMY likely modulates p62 and autophagy crosstalk with the Keap-1/Nrf2 pathway to alleviate liver steatosis and the inflammatory response in the pathological progression of ALD.

Regulation of Cytochrome P450 2B10 (CYP2B10) Expression in Liver by Peroxisome Proliferator-activated Receptor-β/δ Modulation of SP1 Promoter Occupancy

Alcoholic liver disease is a pathological condition caused by overconsumption of alcohol. Because of the high morbidity and mortality associated with this disease, there remains a need to elucidate the molecular mechanisms underlying its etiology and to develop new treatments. Because peroxisome proliferator-activated receptor-β/δ (PPARβ/δ) modulates ethanol-induced hepatic effects, the present study examined alterations in gene expression that may contribute to this disease. Chronic ethanol treatment causes increased hepatic CYP2B10 expression inPparβ/δ^+/+ mice but not in Pparβ/δ^-/- mice. Nuclear and cytosolic localization of the constitutive androstane receptor (CAR), a transcription factor known to regulate Cyp2b10 expression, was not different between genotypes. PPARγ co-activator 1α, a co-activator of both CAR and PPARβ/δ, was up-regulated in Pparβ/δ^+/+ liver following ethanol exposure, but not in Pparβ/δ^-/- liver. Functional mapping of the Cyp2b10 promoter and ChIP assays revealed that PPARβ/δ-dependent modulation of SP1 promoter occupancy up-regulated Cyp2b10 expression in response to ethanol. These results suggest that PPARβ/δ regulates Cyp2b10 expression indirectly by modulating SP1 and PPARγ co-activator 1α expression and/or activity independent of CAR activity. Ligand activation of PPARβ/δ attenuates ethanol-induced Cyp2b10 expression in Pparβ/δ^+/+ liver but not in Pparβ/δ^-/- liver. Strikingly, Cyp2b10 suppression by ligand activation of PPARβ/δ following ethanol treatment occurred in hepatocytes and was mediated by paracrine signaling from Kupffer cells. Combined, results from the present study demonstrate a novel regulatory role of PPARβ/δ in modulating CYP2B10 that may contribute to the etiology of alcoholic liver disease.

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.

Chronic Ethanol-Induced Impairment of Wnt/β-Catenin Signaling is Attenuated by PPAR-δ Agonist

BACKGROUND

The Wnt/β-catenin pathway regulates liver growth, repair, and regeneration. Chronic ethanol (EtOH) exposure blunts normal liver regenerative responses, in part by inhibiting insulin/IGF signaling, and correspondingly, previous studies showed that EtOH-impaired liver regeneration could be restored by insulin sensitizer (proliferator-activated receptor [PPAR]-δ agonist) treatment. As Wnt/β-catenin functions overlap and cross talk with insulin/IGF pathways, we investigated the effects of EtOH exposure and PPAR-δ agonist treatment on Wnt pathway gene expression in relation to liver regeneration.

METHODS

Adult male Long Evans rats were fed with isocaloric liquid diets containing 0 or 37% EtOH for 8 weeks and also treated with vehicle or a PPAR-δ agonist during the last 3 weeks of the feeding regimen. The rats were then subjected to 70% partial hepatectomy (PH) and livers harvested at various post-PH time points were used to quantitate expression of 19 Wnt pathway genes using Quantigene 2.0 Multiplex Assay.

RESULTS

EtOH broadly inhibited expression of Wnt/β-catenin signaling-related genes, including down-regulation of Wnt1, Fzd3, Lef1, and Bcl9 throughout the post-PH time course (0 to 72 hours), and suppression of Wnt7a, Ccnd1, Fgf4, Wif1, Sfrp2, and Sfrp5 at 18- and 24-hour post-PH time points. PPAR-δ agonist treatments rescued the EtOH-induced suppression of Wnt1, Wnt7a, Fzd3, Lef1, Bcl9, Ccnd1, and Sfrp2 gene expression in liver, corresponding with the improvements in DNA synthesis and restoration of hepatic architecture.

CONCLUSIONS

Chronic high-dose EtOH exposures inhibit Wnt signaling, which likely contributes to the impairments in liver regeneration. Therapeutic effects of PPAR-δ agonists extend beyond restoration of insulin/IGF signaling mechanisms and are mediated in part by enhancement of Wnt pathway signaling. Future studies will determine the degree to which targeted restoration of Wnt signaling is sufficient to improve liver regeneration and remodeling in the context of chronic EtOH exposure.

Protective Effect of Hericium erinaceus on Alcohol Induced Hepatotoxicity in Mice

We investigated the effects of Hericium erinaceus (HEM) on liver injury induced by acute alcohol administration in mice. Mice received ethanol (5 g/kg BW) by gavage every 12 hrs for a total of 3 doses. HEM (200 mg/kg BW) was gavage before ethanol administration. Subsequent serum alanine aminotransferase (ALT) level, aspartate aminotransaminase (AST) level, Maleic dialdehyde (MDA) level, hepatic total antioxidant status (TAOS), and activated nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) were determined by ELISA and immunohistochemistry, respectively. HEM administration markedly (P < 0.05) decreased serum ALT, AST, and MDA levels. The hepatic histopathological observations showed that HEM had a relatively significant role in mice model, which had alcoholic liver damage. In conclusion, we observed that HEM (200 mg/kg BW) supplementation could restrain the hepatic damage caused by acute alcohol exposure.

22-S-Hydroxycholesterol protects against ethanol-induced liver injury by blocking the auto/paracrine activation of MCP-1 mediated by LXRα

Chronic ethanol consumption causes hepatic steatosis and inflammation, which are associated with liver hypoxia. Monocyte chemoattractant protein‐1 (MCP‐1) is a hypoxia response factor that determines recruitment and activation of monocytes to the site of tissue injury. The level of MCP‐1 is elevated in the serum and liver of patients with alcoholic liver disease (ALD); however, the molecular details regarding the regulation of MCP‐1 expression are not yet understood completely. Here, we show the role of liver X receptor α (LXRα) in the regulation of MCP‐1 expression during the development of ethanol‐induced fatty liver injury, using an antagonist, 22‐S‐hydroxycholesterol (22‐S‐HC). First, administration of 22‐S‐HC attenuated the signs of liver injury with decreased levels of MCP‐1 and its receptor CCR2 in ethanol‐fed mice. Second, hypoxic conditions or treatment with the LXRα agonist GW3965 significantly induced the expression of MCP‐1, which was completely blocked by treatment with 22‐S‐HC or infection by shLXRα lentivirus in the primary hepatocytes. Third, over‐expression of LXRα or GW3965 treatment increased MCP‐1 promoter activity by increasing the binding of hypoxia‐inducible factor‐1α to the hypoxia response elements, together with LXRα. Finally, treatment with recombinant MCP‐1 increased the level of expression of LXRα and LXRα‐dependent lipid droplet accumulation in both hepatocytes and Kupffer cells. These data show that LXRα and its ligand‐induced up‐regulation of MCP‐1 and MCP‐1‐induced LXRα‐dependent lipogenesis play a key role in the autocrine and paracrine activation of MCP‐1 in the pathogenesis of alcoholic fatty liver disease, and that this activation may provide a promising new target for ALD therapy.Copyright © 2014 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

TLR4 signaling and the inhibition of liver hepcidin expression by alcohol

AIM: To understand the role of toll-like receptor 4 (TLR4) signaling in the regulation of iron-regulatory hormone, hepcidin by chronic alcohol consumption.

METHODS: For chronic alcohol intake studies, TLR4 mutant mice on C3H/HeJ background and wildtype counterpart on C3H/HeOuJ background were pair-fed with regular (control) and ethanol-containing Lieber De Carli liquids diets. Gene expression was determined by real-time quantitative PCR. Protein-protein interactions and protein expression were determined by co-immunoprecipitation and western blotting. The occupancy of hepcidin gene promoter was determined by chromatin immunoprecipitation assays.

RESULTS: Chronic alcohol intake suppressed hepcidin mRNA expression in the livers of wildtype, but not TLR4 mutant, mice. The phosphorylation and nuclear translocation of nuclear factor (NF)-κB p65 subunit protein was observed in alcohol-fed wildtype, but not in alcohol-fed TLR4 mutant, mice. Similarly, alcohol induced the binding of NF-κB p50 subunit protein to hepcidin gene promoter in wildtype, but not in TLR4 mutant, mice. In contrast, the phosphorylation of Stat3 in the liver was stronger in alcohol-treated TLR4 mutant mice compared to alcohol-treated wildtype mice. The occupancy of hepcidin gene promoter by Stat3 was observed in alcohol-fed mutant, but not in wildtype, mice. An interaction between NF-κB p65 subunit protein and small heterodimer partner protein (SHP) was observed in the livers of both wildtype and TLR4 mutant mice fed with the control diet, as shown by co-immunoprecipitation studies. Alcohol intake elevated cytosolic SHP expression but attenuated its interaction with NF-κB in the liver, which was more prominent in the livers of wildtype compared to TLR4 mutant mice.

CONCLUSION: Activation of TLR4 signaling and NF-кB are involved in the suppression of hepcidin gene transcription by alcohol in the presence of inflammation in the liver.

Steatosis and steatohepatitis: complex disorders

Non-alcoholic fatty liver disease (NAFLD) which includes steatosis and steatohepatitis, in particular non-alcoholic steatohepatitis (NASH), is a rising health problem world-wide and should be separated from alcoholic steatohepatitis (ASH). NAFLD is regarded as hepatic manifestation of the metabolic syndrome (MetSy), being tightly linked to obesity and type 2 diabetes mellitus (T2DM). Development of steatosis, liver fibrosis and cirrhosis often progresses towards hepatocellular carcinogenesis and frequently results in the indication for liver transplantation, underlining the clinical significance of this disease complex. Work on different murine models and several human patients studies led to the identification of different molecular key players as well as epigenetic factors like miRNAs and SNPs, which have a promoting or protecting function in AFLD/ASH or NAFLD/NASH. To which extent they might be translated into human biology and pathogenesis is still questionable and needs further investigation regarding diagnostic parameters, drug development and a better understanding of the genetic impact. In this review we give an overview about the currently available knowledge and recent findings regarding the development and progression of this disease.

CMZ reversed chronic ethanol-induced disturbance of PPAR-α possibly by suppressing oxidative stress and PGC-1α acetylation, and activating the MAPK and GSK3β pathway

Background

Cytochrome P4502E1 (CYP2E1) has been suggested to play critical roles in the pathogenesis of alcoholic fatty liver (AFL), but the underlying mechanisms remains unclear. The current study was designed to evaluate whether CYP2E1 suppression by chlormethiazole (CMZ) could suppress AFL in mice, and to explore the underlying mechanisms.

Methods

Mice were treated with or without CMZ (50 mg/kg bw, i.p.) and subjected to liquid diet with or without ethanol (5%, w/v) for 4 weeks. Biochemical parameters were measured using commercial kits. The protein and mRNA levels were detected by western blot and qPCR, respectively. Histopathology and immunohistochemical assay were performed with routine methods.

Results

CYP2E1 inhibition by CMZ completely blocked AFL in mice, shown as the decline of the hepatic and serum triglyceride levels, and the fewer fat droplets in the liver sections. Chronic ethanol exposure led to significant decrease of the mRNA and protein levels of peroxisome proliferator-activated receptor α (PPAR-α), which was blocked by CMZ co-treatment. CMZ co-treatment suppressed ethanol-induced oxidative stress, overproduction of tumor necrosis α (TNF-α), and decrease of protein levels of the PPAR-α co-activators including p300 and deacetylated PGC1-α. Furthermore, CMZ co-treatment led to the activation of AMP-activated protein kinase (AMPK), mitogen-activated protein kinase (MAPK), and PI3K/Akt/GSK3β pathway. However, chronic ethanol-induced decline of acyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) protein levels was partially restored by CMZ, while the activation of autophagy appeared to be suppressed by CMZ.

Conclusion

These results suggested that CMZ suppressed chronic ethanol-induced oxidative stress, TNF-α overproduction, decline of p300 protein level and deacetylation of PGC1-α, and activated AMPK, MAPK, and PI3K/Akt/GSK3β pathway, which might contribute to the activation of PPAR-α and account for the protection of CMZ against AFL.

Dietary nicotinic acid supplementation ameliorates chronic alcohol-induced fatty liver in rats

BACKGROUND

Alcohol abuse frequently causes niacin deficiency in association with the development of alcoholic liver disease. The objective of the present study was to determine whether dietary nicotinic acid (NA) deficiency exaggerates and whether dietary NA supplementation alleviates alcohol-induced fatty liver.

METHODS

Male Sprague-Dawley rats were pair-fed with 4 isocaloric liquid diets: control, ethanol (EtOH), EtOH with dietary NA deficiency, and EtOH with dietary NA supplementation, respectively, for 8 weeks. The control and EtOH diets contained normal levels of NA (7.5 mg/l). Dietary NA deficiency (0 mg NA/l) was achieved by removing NA from the vitamin mix, while NA was added to the liquid diet at 750 mg/l for dietary NA supplementation.

RESULTS

Chronic EtOH feeding induced significant lipid accumulation in the liver, which was not worsened by dietary NA deficiency, but was ameliorated by dietary NA supplementation. Liver total NAD, NAD(+) , and NADH levels were remarkably higher in the NA supplemented group than the NA deficient or EtOH alone groups. Dietary NA supplementation to EtOH-fed rats increased the protein levels of hepatic cytochrome P450 4A1 (CYP4A1) and acyl-coenzyme A oxidase 1 without affecting their mRNA levels. Interestingly, we found dietary NA supplementation reduced the ubiquitination level of CYP4A1. In addition, hepatic fatty acid synthase expression was reduced, while the serum β-hydroxybutyrate and adiponectin concentrations were significantly elevated by dietary NA supplementation. Moreover, dietary NA supplementation modulated EtOH-perturbed liver and serum metabolite profiles.

CONCLUSIONS

These results demonstrate that alcoholic fatty liver was not exaggerated by dietary NA deficiency, but was ameliorated by dietary NA supplementation. Increased hepatic fatty acid oxidation and decreased hepatic de novo lipogenesis contribute to the effects of dietary NA supplementation.

Free radical biology for medicine: learning from nonalcoholic fatty liver disease

Reactive oxygen species, when released under controlled conditions and limited amounts, contribute to cellular proliferation, senescence, and survival by acting as signaling intermediates. In past decades there has been an epidemic diffusion of nonalcoholic fatty liver disease (NAFLD) that represents the result of the impairment of lipid metabolism, redox imbalance, and insulin resistance in the liver. To date, most studies and reviews have been focused on the molecular mechanisms by which fatty liver progresses to steatohepatitis, but the processes leading toward the development of hepatic steatosis in NAFLD are not fully understood yet. Several nuclear receptors, such as peroxisome proliferator-activated receptors (PPARs) α/γ/δ, PPARγ coactivators 1α and 1β, sterol-regulatory element-binding proteins, AMP-activated protein kinase, liver-X-receptors, and farnesoid-X-receptor, play key roles in the regulation of lipid homeostasis during the pathogenesis of NAFLD. These nuclear receptors may act as redox sensors and may modulate various metabolic pathways in response to specific molecules that act as ligands. It is conceivable that a redox-dependent modulation of lipid metabolism, nuclear receptor-mediated, could cause the development of hepatic steatosis and insulin resistance. Thus, this network may represent a potential therapeutic target for the treatment and prevention of hepatic steatosis and its progression to steatohepatitis. This review summarizes the redox-dependent factors that contribute to metabolism alterations in fatty liver with a focus on the redox control of nuclear receptors in normal liver as well as in NAFLD.

ChIP-seq in steatohepatitis and normal liver tissue identifies candidate disease mechanisms related to progression to cancer

Background

Steatohepatitis occurs in alcoholic liver disease and may progress to liver cirrhosis and hepatocellular carcinoma. Its molecular pathogenesis is to a large degree unknown. Histone modifications play a key role in transcriptional regulations as marks for silencing and activation of gene expression and as marks for functional elements. Many transcription factors (TFs) are crucial for the control of the genes involved in metabolism, and abnormality in their function may lead to disease.

Methods

We performed ChIP-seq of the histone modifications H3K4me1, H3K4me3 and H3K27ac and a candidate transcription factor (USF1) in liver tissue from patients with steatohepatitis and normal livers and correlated results to mRNA-expression and genotypes.

Results

We found several regions that are differentially enriched for histone modifications between disease and normal tissue, and qRT-PCR results indicated that the expression of the tested genes strongly correlated with differential enrichment of histone modifications but is independent of USF1 enrichment. By gene ontology analysis of differentially modified genes we found many disease associated genes, some of which had previously been implicated in the etiology of steatohepatitis. Importantly, the genes associated to the strongest histone peaks in the patient were over-represented in cancer specific pathways suggesting that the tissue was on a path to develop to cancer, a common complication to the disease. We also found several novel SNPs and GWAS catalogue SNPs that are candidates to be functional and therefore needs further study.

Conclusion

In summary we find that analysis of chromatin features in tissue samples provides insight into disease mechanisms.

A novel transcription mechanism activated by ethanol: induction of Slc7a11 gene expression via inhibition of the DNA-binding activity of transcriptional repressor octamer-binding transcription factor 1 (OCT-1)

Solute carrier family 7, member 11 (Slc7a11) is a plasma membrane cystine/glutamate exchanger that provides intracellular cystine to produce glutathione, a major cellular antioxidant. Oxidative and endoplasmic reticulum stresses up-regulate Slc7a11 expression by activation of nuclear factor erythroid 2-related factor 2 and transcription factor 4. This study examined the effect of ethanol on Slc7a11 expression and the underlying mechanism involved. Treatment of mouse hepatic stellate cells with ethanol significantly increased Slc7a11 mRNA and protein levels. Deletion of a 20-bp DNA sequence between -2044 to -2024 upstream of the transcription start site significantly increased basal activity and completely abolished the ethanol-induced activity of the Slc7a11 promoter. This deletion did not affect Slc7a11 promoter activity induced by oxidative or endoplasmic reticulum stress. DNA sequence analysis revealed a binding motif for octamer-binding transcription factor 1 (OCT-1) in the deleted fragment. Mutation of this OCT-1 binding motif resulted in a similar effect as the deletion experiment, i.e. it increased the basal promoter activity and abolished the response to ethanol. Ethanol exposure significantly inhibited OCT-1 binding to the Slc7a11 promoter region, although it did not alter OCT-1 mRNA and protein levels. OCT-1 reportedly functions as either a transcriptional enhancer or repressor, depending on the target genes. Results from this study suggest that OCT-1 functions as a repressor on the Slc7a11 promoter and that ethanol inhibits OCT-1 binding to the Slc7a11 promoter, thereby increasing Slc7a11 expression. Taken together, inhibition of the DNA binding activity of transcriptional repressor OCT-1 is a mechanism by which ethanol up-regulates Slc711 expression.

Chronic alcohol-induced hepatic insulin resistance and endoplasmic reticulum stress ameliorated by peroxisome-proliferator activated receptor-δ agonist treatment

BACKGROUND AND AIM

Chronic alcoholic liver disease is associated with hepatic insulin resistance, dysregulated lipid metabolism with increased toxic lipid (ceramide) accumulation, lipid peroxidation, and oxidative and endoplasmic reticulum (ER) stress. Peroxisome-proliferator activated receptor (PPAR) agonists are insulin sensitizers that can restore hepatic insulin responsiveness in both alcohol and non-alcohol-related steatohepatitis. Herein, we demonstrate that treatment with a PPAR-δ agonist enhances insulin signaling and reduces the severities of ER stress and ceramide accumulation in an experimental model of ethanol-induced steatohepatitis.

METHODS

Adult male Long Evans rats were pair fed with isocaloric liquid diets containing 0% or 37% ethanol (caloric) for 8 weeks. After 3 weeks on the diets, rats were treated with vehicle or PPAR-δ agonist twice weekly by i.p. injection.

RESULTS

Ethanol-fed rats developed steatohepatitis with inhibition of signaling through the insulin and insulin-like growth factor-1 receptors, and Akt activated pathways. Despite continued ethanol exposure, PPAR-δ agonist co-treatments increased Akt activation, reduced multiple molecular indices of ER stress and steatohepatitis.

CONCLUSIONS

These results suggest that PPAR-δ agonist rescue of chronic alcoholic liver disease is mediated by enhancement of insulin signaling through Akt/metabolic pathways that reduce lipotoxicity and ER stress.

Preservation of hepatocyte nuclear factor-4α contributes to the beneficial effect of dietary medium chain triglyceride on alcohol-induced hepatic lipid dyshomeostasis in rats

BACKGROUND

Alcohol consumption is a major cause of fatty liver, and dietary saturated fats have been shown to protect against alcoholic fatty liver. This study investigated the mechanisms of how dietary saturated fat may modulate alcohol-induced hepatic lipid dyshomeostasis.

METHODS

Male Sprague Dawley rats were pair-fed with 3 isocaloric liquid diets, control, alcohol, and medium chain triglyceride (MCT)/alcohol, respectively, for 8 weeks. The control and alcohol diets were based on the Lieber-DeCarli liquid diet formula with 30% total calories derived from corn oil (rich in unsaturated long chain fatty acids). The corn oil was replaced by MCT, which consists of exclusive saturated fatty acids, in the MCT/alcohol diet. HepG2 cell culture was conducted to test the effects of unsaturated fatty acids on hepatocyte nuclear factor-4α (HNF4α) and the role of HNF4α in regulating hepatocyte lipid homeostasis.

RESULTS

Alcohol feeding caused significant lipid accumulation, which was attenuated by dietary MCT. The major effect of alcohol on hepatic gene expression is the up-regulation of CYP4A1, CD36, and GPAT3, and down-regulation of apolipoprotein B (ApoB). Dietary MCT further up-regulated CYP4A1 gene, normalized ApoB gene, and up-regulated MTTP and SCD1 genes. The protein level of HNF4α, a master transcription factor of the liver, was reduced by alcohol feeding, which was normalized by dietary MCT. Fatty acid profiling demonstrated that alcohol feeding dramatically increased hepatic unsaturated long chain fatty acyl species, particularly linoleic acid and oleic acid, which was attenuated by dietary MCT. Dietary MCT attenuated alcohol-reduced serum triglyceride level and modulated the fatty acid composition of the serum triglycerides. Cell culture study demonstrated polyunsaturated linoleic acid rather than monounsaturated oleic acid inactivated HNF4α in HepG2 cells. Knockdown of HNF4α caused lipid accumulation in HepG2 cells due to dysregulation of very low density lipoprotein secretion.

CONCLUSIONS

Results suggest that dietary MCT prevents alcohol-induced hepatic lipid accumulation, at least partially, through reducing hepatic polyunsaturated long chain fatty acids and preserving HNF4α.

Association of liver stiffness with hepatic expression of pharmacokinetically important genes in alcoholic liver disease

BACKGROUND

Enhanced drug elimination in alcoholics remains largely indefinable. In contrast, the reduced elimination of drugs in patients with advanced alcoholic liver disease (ALD) is normally owing to hepatic end-stage disease such as cirrhosis. We here study the mRNA expression of various hepatic drug metabolizing enzymes and transporters in association with liver stiffness (LS) being a novel noninvasive parameter for the assessment of cirrhosis to unravel the dynamic relationship between ALD and determinants of pharmacokinetics such as drug metabolizing enzymes and transporters.

METHODS

We quantified mRNA expression levels of various cytochrome P-450 isoenzymes (CYPs) and drug transporters in 26 liver specimens of chronic alcoholics and 5 controls by quantitative polymerase chain reaction. In addition, liver histology, clinical data, and LS evaluated by transient elastography (Fibroscan) were obtained.

RESULTS

Eighteen patients had a normal or moderate LS < 8 kPa (69.2%), while in the remaining 8 patients (30.7%) advanced F3 or F4 fibrosis could be established with an LS > 8 kPa. Overall, CYP3A4, CYP2E1, and solute carrier organic anion transporter 1B1 (SLCO1B1) were negatively correlated with increasing LS. CYPs and drug transporters tended to be up-regulated in alcoholics without advanced fibrosis (LS < 8.0 kPa) compared to healthy controls supporting data of boosted drug elimination in alcoholics without advanced ALD. However, in alcoholics with severely increased LS (>8 kPa), expression levels of CYP2E1, SLC22A2, and SLCO1B1 were significantly lower.

CONCLUSIONS

In conclusion, CYPs and drug transporters seem to be induced in chronic alcoholics without irreversible liver damage but decline in case of manifest cirrhosis. Our study also suggests that noninvasive measurements of LS could be useful for pharmacokinetic predictions and individualized pharmacotherapy.

Suppression of the Nrf2-dependent antioxidant response by glucocorticoids and 11β-HSD1-mediated glucocorticoid activation in hepatic cells

Background

Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is a key transcription factor regulating a plethora of detoxifying enzymes and antioxidant genes involved in drug metabolism and defence against oxidative stress. The glucocorticoid receptor (GR) is a ligand-induced transcription factor involved in the regulation of energy supply for metabolic needs to cope with various stressors. GR activity is controlled by glucocorticoids, which are synthesized in the adrenal glands and regenerated mainly in the liver from inactive cortisone by 11β-hydroxysteroid dehydrogenase-1 (11β-HSD1).

Methods and Principal Findings

Using transfected HEK-293 cells and hepatic H4IIE cells we show that glucocorticoids, activated by 11β-HSD1 and acting through GR, suppress the Nrf2-dependent antioxidant response. The expression of the marker genes NQO1, HMOX1 and GST2A was suppressed upon treatment of 11β-HSD1 expressing cells with cortisone, an effect that was reversed by 11β-HSD1 inhibitors. Furthermore, our results demonstrate that elevated glucocorticoids lowered the ability of cells to detoxify H₂O₂. Moreover, a comparison of gene expression in male and female rats revealed an opposite sexual dimorphism with an inverse relationship between 11β-HSD1 and Nrf2 target gene expression.

Conclusions

The results demonstrate a suppression of the cellular antioxidant defence capacity by glucocorticoids and suggest that elevated 11β-HSD1 activity may lead to impaired Nrf2-dependent antioxidant response. The gender-specific differences in hepatic expression levels of 11β-HSD1 and Nrf2 target genes and the impact of pharmacological inhibition of 11β-HSD1 on improving cellular capacity to cope with oxidative stress warrants further studies in vivo.

Oxidative stress and redox signaling mechanisms of alcoholic liver disease: updated experimental and clinical evidence

Alcoholic liver disease (ALD) is a major cause of morbidity and mortality in the United States and Europe. The spectrum of ALD ranges from fatty liver to alcoholic hepatitis and cirrhosis, which may eventually lead to hepatocellular carcinoma. In developed countries as well as developing nations, ALD is a major cause of end-stage liver disease that requires liver transplantation. The most effective therapy for ALD is alcohol abstinence; however, for individuals with severe ALD and those in whom alcohol abstinence is not achievable, targeted therapies are absolutely necessary. In this context, advances of our understanding of the pathophysiology of ALD over the past two decades have contributed to the development of therapeutic modalities (e.g., pentoxifylline and corticosteroids) for the disease although the efficacy of the available treatments remains limited. This article is intended to succinctly review the recent experimental and clinical findings of the involvement of oxidative stress and redox signaling in the pathophysiology of ALD and the development of mechanistically based antioxidant modalities targeting oxidative stress and redox signaling mechanisms. The biochemical and cellular sources of reactive oxygen and nitrogen species (ROS/RNS) and dysregulated redox signaling pathways associated with alcohol consumption are particularly discussed to provide insight into the molecular basis of hepatic cell dysfunction and destruction as well as tissue remodeling underlying ALD.

Structural Correlates of PPAR Agonist Rescue of Experimental Chronic Alcohol-Induced Steatohepatitis

Chronic alcoholic liver disease is associated with hepatic insulin resistance, inflammation, oxidative and ER stress, mitochondrial dysfunction, and DNA damage. Peroxisome-proliferator activated receptor (PPAR) agonists are insulin sensitizers that have anti-inflammatory/anti-oxidant effects. We previously showed that PPAR agonists can restore hepatic insulin responsiveness in chronic ethanol-fed rats with steatohepatitis. Herein, we furthered our investigations by characterizing the histological and ultrastructural changes mediated by PPAR agonist rescue of alcohol-induced steatohepatitis. Adult male Long Evans rats were pair fed with isocaloric liquid diets containing 0% or 37% ethanol (caloric) for 8 weeks. After 3 weeks on the diets, rats were treated with vehicle, or a PPAR-α, PPAR-δ, or PPAR-γ agonist twice weekly by i.p. injection. Ethanol-fed rats developed steatohepatitis with disordered hepatic chord architecture, mega-mitochondria, disruption of the RER, increased apoptosis, and increased 4-hydroxynonenal (HNE) and 3-nitrotyrosine (NTyr) immunoreactivity. PPAR-δ and PPAR-γ agonists reduced the severity of steatohepatitis, and restored the hepatic chord-like architectural, mitochondrial morphology, and RER organization, and the PPAR-δ agonist significantly reduced hepatic HNE. On the other hand, prominent RER tubule dilation, which could reflect ER stress, persisted in ethanol-exposed, PPAR-γ treated but not PPAR-δ treated livers. The PPAR-α agonist exacerbated both steatohepatitis and formation of mega-mitochondria, and it failed to restore RER architecture or lower biochemical indices of oxidative stress. In conclusion, improved hepatic insulin responsiveness and decreased inflammation resulting from PPAR-δ or PPAR-γ agonist treatments of alcohol-induced steatohepatitis are likely mediated by enhanced signaling through metabolic pathways with attendant reductions in ER stress, oxidative stress, and mitochondrial dysfunction.

Alteration of hepatic nuclear receptor-mediated signaling pathways in hepatitis C virus patients with and without a history of alcohol drinking

The current study tests a hypothesis that nuclear receptor signaling is altered in chronic hepatitis C patients and that the altered pattern is specific to alcohol drinking history. The expression of a panel of more than 100 genes encoding nuclear receptors, coregulators, and their direct/indirect targets was studied in human livers. Gene expression pattern was compared between 15 normal donor livers and 23 hepatitis C virus (HCV) genotype 1-positive livers from patients without a drinking history (matched for age, sex, and body mass index). HCV infection increased the expression of nuclear receptors small heterodimer partner and constitutive androstane receptor (CAR) as well as genes involved in fatty acid trafficking, bile acid synthesis and uptake, and inflammatory response. However, the expression of retinoid X receptor (RXR) α, peroxisomal proliferator-activated receptor (PPAR) α and β as well as steroid regulatory element-binding protein (SREBP)-1c was decreased in HCV-infected livers. Gene expression pattern was compared in chronic hepatitis C patients with and without a drinking history. Alcohol drinking increased the expression of genes involved in fatty acid uptake, trafficking, and oxidation, but decreased the expression of genes responsible for gluconeogenesis. These changes were consistent with reduced fasting plasma glucose levels and altered expression of upstream regulators that include RXRα, PPARα, and CAR. The messenger RNA levels of fibroblast growth factor 21, interleukin-10, and fatty acid synthase, which are all regulated by nuclear receptors, showed independent correlation with hepatic HCV RNA levels.

CONCLUSION

Our findings suggest that those genes and pathways that showed altered expression could potentially be therapeutic targets for HCV infection and/or alcohol drinking-induced liver injury.

The burden of cancer attributable to alcohol consumption

Many epidemiological studies have demonstrated a correlation between alcohol intake and the occurrence of cancer in humans. All types of alcoholic beverages are associated with an increased risk which suggests that ethanol itself is the crucial compound which causes that effect.The International Agency for Research for Cancer classified alcohol consumption and acetaldehyde associated with alcohol consumption as carcinogenic for humans (group 1): oral cavity, pharynx, larynx, esophagus, colorectal, liver and female breast.THE MECHANISMS BY WHICH ALCOHOL CONSUMPTION EXERTS ITS CARCINOGENIC EFFECT HAVE NOT BEEN DEFINED FULLY, ALTHOUGH PLAUSIBLE EVENTS INCLUDE: a genotoxic effect of acetaldehyde; increased estrogen concentration, which is important for breast carcinogenesis; a role as solvent of tobacco carcinogens; production of reactive oxygen species and nitrogen species; and change in folate metabolism.Most alcohol-induced diseases increases in a linear fashion as intake increases: oral, esophagus and colon cancer fall into this pattern: very little is known about safe margins of alcohol consumption. Given the linear dose-response relation between alcohol intake and risk of cancer, control of heavy drinking remains the main target for cancer control.In healthy subjects, European Code Against Cancer recommends keeping daily consumption within two drinks for man and one drink for women.In our opinion, there are not enough data to support the actually safe intake of alcohol. Any level of alcohol consumption increase the risk of developing an alcohol related cancer. The level of risk increases in line with the level consumption.

Altered hepatic lipid metabolism in C57BL/6 mice fed alcohol: a targeted lipidomic and gene expression study

Chronic alcohol consumption is associated with fatty liver disease in mammals. The object of this study was to gain an understanding of dysregulated lipid metabolism in alcohol-fed C57BL/6 mice using a targeted lipidomic approach. Liquid chromatography tandem mass spectrometry was used to analyze several lipid classes, including free fatty acids, fatty acyl-CoAs, fatty acid ethyl esters, sphingolipids, ceramides, and endocannabinoids, in plasma and liver samples from control and alcohol-fed mice. The interpretation of lipidomic data was augmented by gene expression analyses for important metabolic enzymes in the lipid pathways studied. Alcohol feeding was associated with i) increased hepatic free fatty acid levels and decreased fatty acyl-CoA levels associated with decreased mitochondrial fatty acid oxidation and decreased fatty acyl-CoA synthesis, respectively; ii) increased hepatic ceramide levels associated with higher levels of the precursor molecules sphingosine and sphinganine; and iii) increased hepatic levels of the endocannabinoid anandamide associated with decreased expression of its catabolic enzyme fatty acid amide hydrolase. The unique combination of lipidomic and gene expression analyses allows for a better mechanistic understanding of dysregulated lipid metabolism in the development of alcoholic fatty liver disease.

Polyphenols in alcoholic beverages activating constitutive androstane receptor CAR

The constitutive androstane receptor CAR is a xenosensing nuclear receptor that can be activated by natural polyphenols such as flavonoids and catechins. We examined alcoholic beverage phytochemicals for their ability to activate CAR. HepG2 cells were transfected with CAR expression vector and its reporter gene, and then treated with trans-resveratrol, ellagic acid, β-caryophyllene, myrcene, and xanthohumol. A luciferase assay revealed that ellagic acid and trans-resveratrol activated both human and mouse CAR. Since CAR regulates many genes involved in energy metabolism, the possibility exists that these polyphenols would reduce the risk of certain alcohol-induced metabolic disorders with the help of CAR.

Data mining reveals complex interactions of risk factors and clinical feature profiling associated with the staging of non-hepatitis B virus/non-hepatitis C virus-related hepatocellular carcinoma

AIM

  Non-hepatitis B virus/non-hepatitis C virus-related hepatocellular carcinoma (NBNC-HCC) is often detected at an advanced stage, and the pathology associated with the staging of NBNC-HCC remains unclear. Data mining is a set of statistical techniques which uncovers interactions and meaningful patterns of factors from a large data collection. The aims of this study were to reveal complex interactions of the risk factors and clinical feature profiling associated with the staging of NBNC-HCC using data mining techniques.

METHODS

  A database was created from 663 patients with NBNC-HCC at 20 institutions. The Milan criteria were used as staging of HCC. Complex associations of variables and clinical feature profiling with the Milan criteria were analyzed by graphical modeling and decision tree algorithm methods, respectively.

RESULTS

  Graphical modeling identified six factors independently associated with the Milan criteria: diagnostic year of HCC; diagnosis of liver cirrhosis; serum aspartate aminotransferase (AST); alanine aminotransferase (ALT); α-fetoprotein (AFP); and des-γ-carboxy prothrombin (DCP) levels. The decision trees were created with five variables to classify six groups of patients. Sixty-nine percent of the patients were within the Milan criteria, when patients showed an AFP level of 200 ng/mL or less, diagnosis of liver cirrhosis and an AST level of less than 93 IU/mL. On the other hand, 18% of the patients were within the Milan criteria, when patients showed an AFP level of more than 200 ng/mL and ALT level of 20 IU/mL or more.

CONCLUSION

  Data mining disclosed complex interactions of the risk factors and clinical feature profiling associated with the staging of NBNC-HCC.

The interaction between HCV and nuclear receptor-mediated pathways

Hepatitis C virus (HCV) is presently the leading indication for liver transplantation in Western countries. Treatment for HCV infection includes a combination of pegylated interferon and ribavirin, which produces highly variable response rates. This reflects the lack of information regarding the roles of host and viral components during viral pathogenesis. Vital processes regulated by the liver, including metabolism, lipid homeostasis, cellular proliferation, and the immune response, are known to be systematically dysregulated as a result of persistent HCV infection. Nuclear receptors and their ligands are recognized as indispensable regulators of liver homeostasis. Pathways mediated by the nuclear receptor superfamily have been shown to be profoundly disrupted during HCV infection, leading to an increased importance in elucidating the exact nature of this complex relationship. Expanded understanding of the role of nuclear receptors in HCV infection may therefore be an essential step in the search for a more universally effective treatment.

Fibrosis in alcoholic and nonalcoholic steatohepatitis

Both alcoholic and nonalcoholic steatohepatitis are relevant causes of cirrhosis and liver-related mortality. Alcohol abuse represents a major health problem in many countries, and liver disease is considered one of the most relevant causes of death related to this factor. Nonalcoholic fatty liver disease is the most common hepatic abnormality in the Western world, and progresses to cirrhosis and hepatocellular carcinoma in a significant portion of cases. Moreover, presence of NAFLD is associated with an increased risk of cardiovascular events. In this review, we discuss the characteristics of fibrosis in alcoholic and nonalcoholic steatohepatitis, focussing on the diagnostic issues and predictive factors. In addition, the pathogenetic mechanisms responsible for appearance and progression of fibrosis in the two conditions are briefly discussed.

Effect of soyasaponins-rich extract from soybean on acute alcohol-induced hepatotoxicity in mice

The protective effects of soyasaponins-rich extract (SRE) from soybean against acute alcohol-induced hepatotoxicity were first investigated in the Institute of Cancer Research mice. Administration of SRE prior to alcohol significantly prevented the increases in serum aspartate transaminase, alanine transaminase, alkaline phosphatase, and lactate dehydrogenase caused by alcohol, as well as hepatic triglyceride, total cholesterol, and malondialdehyde levels. Mice treated with SRE showed a better profile of the antioxidant system with normal superoxide dismutase, glutathione S-transferase, and glutathione peroxidase activities, which were associated with the increase of hepatic glutathione levels relative to the acute alcohol-treated group. Supplement of SRE prevented alcohol-induced hepatic steatosis necrosis, inflammation, and swelling, as indicated by liver histopathological studies. All of these findings demonstrate that SRE has protective effects on acute alcohol-induced liver damage.

Retinoid pathway and cancer therapeutics

The retinoids are a class of compounds that are structurally related to vitamin A. Retinoic acid, which is the active metabolite of retinol, regulates a wide range of biological processes including development, differentiation, proliferation, and apoptosis. Retinoids exert their effects through a variety of binding proteins including cellular retinol-binding protein (CRBP), retinol-binding proteins (RBP), cellular retinoic acid-binding protein (CRABP), and nuclear receptors i.e. retinoic acid receptor (RAR) and retinoid x receptor (RXR). Because of the pleiotropic effects of retinoids, understanding the function of these binding proteins and nuclear receptors assists us in developing compounds that have specific effects. This review summarizes our current understanding of how retinoids are processed and act with an emphasis on the application of retinoids in cancer treatment and prevention.