Nrf2 in alcoholic liver disease

Oxidative stress in alcoholic liver disease, focusing on proteins, nucleic acids, and lipids: A review

Oxidative stress is one of the important factors in the development of alcoholic liver disease. The production of reactive oxygen species and other free radicals is an important feature of alcohol metabolism in the liver and an important substance in liver injury. When large amounts of ROS are produced, the homeostasis of the liver REDOX system will be disrupted and liver injury will be caused. Oxidative stress can damage proteins, nucleic acids and lipids, liver dysfunction. In addition, damaging factors produced by oxidative damage to liver tissue can induce the occurrence of inflammation, thereby aggravating the development of ALD. This article reviews the oxidative damage of alcohol on liver proteins, nucleic acids, and lipids, and provides new insights and summaries of the oxidative stress process. We also discussed the relationship between oxidative stress and inflammation in alcoholic liver disease from different perspectives. Finally, the research status of antioxidant therapy in alcoholic liver disease was summarized, hoping to provide better help for learning and developing the understanding of alcoholic liver disease.

A Butyrate-Yielding Dietary Supplement Prevents Acute Alcoholic Liver Injury by Modulating Nrf2-Mediated Hepatic Oxidative Stress and Gut Microbiota

Alcoholic liver disease (ALD) is a globally prevalent form of liver disease for which there is no effective treatment. Recent studies have found that a significant decrease in butyrate was closely associated with ALD development. Given the low compliance and delivery efficiency associated with oral-route butyrate administration, a highly effective butyrate-yielding dietary supplement, butyrylated high-amylose maize starch (HAMSB), is a good alternative approach. Here, we synthesized HAMSB, evaluated the effect of HAMSB on acute ALD in mice, compared its effect with that of oral administration of butyrate, and further studied the potential mechanism of action. The results showed HAMSB alleviated acute ALD in mice, as evidenced by the inhibition of hepatic-function impairment and the improvement in liver steatosis and lipid metabolism; in these respects, HAMSB supplementation was superior to oral sodium butyrate administration. These improvements can be attributed to the reduction of oxidative stress though the regulation of Nrf2-mediated antioxidant signaling in the liver and the improvement in the composition and function of microbiota in the intestine. In conclusion, HAMSB is a safe and effective dietary supplement for preventing acute ALD that could be useful as a disease-modifying functional food or candidate medicine.

Procyanidin B2-3'-O-Gallate Derived from Grape Seed Polymeric Procyanidins via the Galloyl-Attached Nucleophilic Degradation as a Potential Hepatoprotective Agent

An effective method was developed for preparing galloylated procyanidins (GPCs) using galloyl-attached nucleophilic degradation. Under degradation conditions optimized through Box-Behnken design and single-factor experiments, two dimeric and three tetrameric GPCs were produced, with the yield of procyanidin B2-3'-O-gallate (B2-3'-G) reaching up to 232 mg/g (PPCs). The structure of B2-3'-G was identified by UV, FTIR, NMR, CD, MS, and phloroglucinolysis. Furthermore, the protective effect of B2-3'-G against alcohol-induced liver injury (ALI) was investigated. Compared with the parent compounds, B2-3'-G exhibited a stronger capacity for inhibiting ALI, attributed to its polymerization degree and galloyl group. Subsequent experiments revealed that the pretreatment of BRL-3A cells with B2-3'-G prior to ethanol improved ALI through activation of the Nrf2-HO-1/NQO1 pathway and initiation of enzymatic antioxidant systems. These findings suggest that GPC B2-3'-G is a potential hepatoprotective agent, which provides a new perspective for functional development of GPCs.

The Flavonoid Glycoside from Abrus cantoniensis Hance Alleviates Alcoholic Liver Injury by Inhibiting Ferroptosis in an AMPK-Dependent Manner

Abrus cantoniensis Hance is a vegetative food and can be used as a folk beverage or soup to clear liver toxins and prevent liver damage. However, the components and effects of A. cantoniensis Hance in alcohol-induced liver injury were unknown. This study aimed to obtain abundant phytochemicals from A. cantoniensis Hance and identify the potency of the isolates in preventing alcohol-induced liver injury. Alcohol-stimulated AML12 cells and Lieber-DeCarli diet-fed mice were used to establish in vitro and in vivo models, respectively. Our findings indicated that flavonoid glycosides, especially AH-15, could significantly alleviate alcohol-induced liver injury by inhibiting oxidative stress. Furthermore, we demonstrated that AH-15 inhibited ferroptosis induced by lipid peroxidation. Mechanically, we found that AH-15 regulated nuclear factor erythroid 2-related factor 2 (NRF2) expression via activation of AMP-activated protein kinase (AMPK) signaling. These results indicate that A. cantoniensis Hance is a great potential functional food for alleviating alcohol-induced liver injury.

Mimicking chronic alcohol effects through a controlled and sustained ethanol release device

Alcohol consumption, a pervasive societal issue, poses considerable health risks and socioeconomic consequences. Alcohol-induced hepatic disorders, such as fatty liver disease, alcoholic hepatitis, chronic hepatitis, liver fibrosis, and cirrhosis, underscore the need for comprehensive research. Existing challenges in mimicking chronic alcohol exposure in cellular systems, attributed to ethanol evaporation, necessitate innovative approaches. In this study, we developed a simple, reusable, and controllable device for examining the physiological reactions of hepatocytes to long-term alcohol exposure. Our approach involved a novel device designed to continuously release ethanol into the culture medium, maintaining a consistent ethanol concentration over several days. We evaluated device performance by examining gene expression patterns and cytokine secretion alterations during long-term exposure to ethanol. These patterns were correlated with those observed in patients with alcoholic hepatitis. Our results suggest that our ethanol-releasing device can be used as a valuable tool to study the mechanisms of chronic alcohol-mediated hepatic diseases at the cellular level. Our device offers a practical solution for studying chronic alcohol exposure, providing a reliable platform for cellular research. This innovative tool holds promise for advancing our understanding of the molecular processes involved in chronic alcohol-mediated hepatic diseases. Future research avenues should explore broader applications and potential implications for predicting and treating alcohol-related illnesses.

The Role of Oxidative Stress in Alcoholic Fatty Liver Disease: A Systematic Review and Meta-Analysis of Preclinical Studies

Alcoholic Fatty Liver Disease (AFLD) is characterized by the accumulation of lipids in liver cells owing to the metabolism of ethanol. This process leads to a decrease in the NAD+/NADH ratio and the generation of reactive oxygen species. A systematic review and meta-analysis were conducted to investigate the role of oxidative stress in AFLD. A total of 201 eligible manuscripts were included, which revealed that animals with AFLD exhibited elevated expression of CYP2E1, decreased enzymatic activity of antioxidant enzymes, and reduced levels of the transcription factor Nrf2, which plays a pivotal role in the synthesis of antioxidant enzymes. Furthermore, animals with AFLD exhibited increased levels of lipid peroxidation markers and carbonylated proteins, collectively contributing to a weakened antioxidant defense and increased oxidative damage. The liver damage in AFLD was supported by significantly higher activity of alanine and aspartate aminotransferase enzymes. Moreover, animals with AFLD had increased levels of triacylglycerol in the serum and liver, likely due to reduced fatty acid metabolism caused by decreased PPAR-α expression, which is responsible for fatty acid oxidation, and increased expression of SREBP-1c, which is involved in fatty acid synthesis. With regard to inflammation, animals with AFLD exhibited elevated levels of pro-inflammatory cytokines, including TNF-a, IL-1β, and IL-6. The heightened oxidative stress, along with inflammation, led to an upregulation of cell death markers, such as caspase-3, and an increased Bax/Bcl-2 ratio. Overall, the findings of the review and meta-analysis indicate that ethanol metabolism reduces important markers of antioxidant defense while increasing inflammatory and apoptotic markers, thereby contributing to the development of AFLD.

The protective effect of Enteromorpha prolifera polysaccharide on alcoholic liver injury in C57BL/6 mice

An alcohol-induced liver injury model was induced in C57BL/6 mice to assess the protective efficacy of Enteromorpha prolifera polysaccharides (EP) against liver damage. Histological alterations in the liver were examined following hematoxylin-eosin (H&E) staining. Biochemical assay kits and ELISA kits were employed to analyze serum and liver biochemical parameters, as well as the activity of antioxidant enzymes and alcohol metabolism-related enzymes. The presence of oxidative stress-related proteins in the liver was detected using western blotting. Liquid chromatography and mass spectrometry were used to profile serum metabolites in mice. The findings demonstrated that EP-H (100 mg/Kg) reduced serum ALT and AST activity by 2.31-fold and 2.32-fold, respectively, when compared to the alcohol-induced liver injury group. H&E staining revealed a significant attenuation of microvesicular steatosis and ballooning pathology in the EP-H group compared to the model group. EP administration was found to enhance alcohol metabolism by regulating metabolite-related enzymes (ADH and ALDH) and decreasing CYP2E1 expression. EP also modulated the Nrf2/HO-1 signaling pathway to bolster hepatic antioxidant capacity. Furthermore, EP restored the levels of lipid metabolites (Glycine, Butanoyl-CoA, and Acetyl-CoA) to normalcy. In summary, EP confers protection to the liver through the regulation of antioxidant activity and lipid metabolites in the murine liver.

Hepatoprotective Effect of Annulohypoxylon stygium Melanin on Acute Alcoholic Liver Injury in Mice

Annulohypoxylon stygium melanin (AsM) has various functional properties such as antioxidant and anti-radiation, but its biological activity in vivo has not been fully investigated. In this study, we researched the effects of AsM on the protection against acute liver injury in mice and its mechanism. The results showed that AsM had no significant effect on body weight in mice but reduced the liver index. It was able to significantly decrease the activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT), the contents of triglyceride (TG) and total cholesterol (TC) in mice. Simultaneously, it raised the levels of superoxide dismutase (SOD), peroxidase (CAT), and glutathione peroxidase (GSH-Px), which obviously exceeded those of the EtOH group. AsM could significantly lower the levels of inflammatory factors, with inhibition rates of 68.30%, 29.0%, and 19.50% for IL-1β, IL-6, and TNF-α, respectively. H&E and Oil red O staining also showed that AsM ameliorated liver damage and lipid accumulation in mice. The protective mechanism of AsM may be associated to the nuclear factor erythroid 2-related factor 2 (Nrf2) antioxidant signaling pathway, which could activate the downstream antioxidant enzymes heme oxygenase-1 (HO-1), glutamate-cysteine ligase modifier subunit (GCLM), and glutamate-cysteine ligase catalytic subunit (GCLC). These findings confirmed that AsM had an alleviating effect on alcoholic liver injury and provided new thoughts for the development of natural product.

Glucosamine attenuates alcohol-induced acute liver injury via inhibiting oxidative stress and inflammation

Alcohol liver disease (ALD) is a liver disease caused by long-term heavy drinking. Glucosamine (GLC) is an amino monosaccharide that plays a very important role in the synthesis of human and animal cartilage. GLC is commonly used in the treatment of mild to moderate osteoarthritis and has good anti-inflammatory and antioxidant properties. In this study, alcoholic injury models were constructed in mice and human normal hepatocyte L02 cells to explore the protective effect and mechanism of GLC on ALD. Mice were given GLC by gavage for 30 days. Liver injury models of both mice and L02 cells were produced by ethanol. Detecting the levels of liver injury biomarkers, lipid metabolism, oxidative stress biomarkers, and inflammatory factors through different reagent kits. Exploring oxidative and inflammatory pathways in mouse liver tissue through Western blot and RT-PCR. The results showed that GLC can significantly inhibit the abnormal increase of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), triglycerides (TG), total cholesterol (TC), very low density lipoprotein (VLDL), low-density lipoprotein cholesterol (LDL-C), and can significantly improve the level of high-density lipoprotein cholesterol (HDL-C). In addition, GLC intervention significantly improved alcohol induced hepatic oxidative stress by reducing the levels of malondialdehyde (MDA) and, increasing the levels of glutathione (GSH), catalase (CAT) and superoxide dismutase (SOD) in the liver. Further mechanisms suggest that GLC can inhibit the expression of ethanol metabolism enzyme cytochrome P4502E1 (CYP2E1), activate the antioxidant pathway Keap1/Nrf2/HO-1, down-regulate the phosphorylation of MAPK and NF-κB signaling pathways, and thus reduce the expression of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6). Therefore, GLC may be a significant candidate functional food for attenuating alcohol induced acute liver injury.

FXR overexpression prevents hepatic steatosis through inhibiting AIM2 inflammasome activation in alcoholic liver disease

BACKGROUND AND PURPOSE

Alcoholic liver disease (ALD), a metabolic liver disease caused by excessive alcohol consumption, has attracted increasing attention due to its high prevalence and mortality. Up to date, there is no effective and feasible treatment method for ALD. This study was to investigate whether Farnesoid X receptor (FXR, NR1H4) can alleviate ALD and whether this effect is mediated by inhibiting absent in melanoma 2 (AIM2) inflammasome activation.

METHODS

The difference in FXR expression between normal subjects and ALD patients was analyzed using the Gene Expression Omnibus (GEO) database. Lieber-DeCarli liquid diet with 5% ethanol (v/v) (EtOH) was adopted to establish the mouse ALD model. Liver histopathological changes and the accumulation of lipid droplets were assessed by H&E and Oil Red O staining. Quantitative real-time PCR, Western blotting analysis and immunofluorescence staining were utilized to evaluate the expression levels of related genes and proteins. DCFH-DA staining was adopted to visualize reactive oxidative species (ROS).

RESULTS

FXR was distinctly downregulated in liver tissues of patients with steatosis compared to normal livers using the GEO database, and in ethanol-induced AML-12 cellular steatosis model. FXR overexpression ameliorated hepatic lipid metabolism disorder and steatosis induced by ethanol by inhibiting the expression of genes involved in lipid synthesis and inducing the expression of genes responsible for lipid metabolism. Besides, FXR overexpression inhibited ethanol-induced AIM2 inflammasome activation and alleviated oxidative stress and ROS production during ethanol-induced hepatic steatosis. However, when FXR was knocked down, the results were completely opposite.

CONCLUSIONS

FXR attenuated lipid metabolism disorders and lipid degeneration in alcohol-caused liver injury and alleviated oxidative stress and inflammation by inhibiting AIM2 inflammasome activation.

The gut-liver axis perspective: Exploring the protective potential of polysaccharides from Cistanche deserticola against alcoholic liver disease

The primary objective of this study is to investigate the potential mechanism behind the protective effect of Cistanche deserticola polysaccharides (CP) against alcoholic liver disease (ALD). Multiple chromography techniques were employed to characterize CP from polysaccharide, the molecular weight distribution of polysaccharides, monosaccharide composition, isomeric hydrogen and isomeric carbon, in order to clarify the material basis of CP. To create the ALD mouse model, we utilized the well-established Lieber-DeCarli alcoholic liquid feed method. Findings from the study revealed that CP administration resulted in significant improvements in intestinal permeability, upregulation of barrier proteins expression, and reduced levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in mouse liver and serum. Additionally, CP treatment reduced the presence of inflammatory cytokines both in serum and liver while enhancing the activity of antioxidant enzymes in the liver. Furthermore, CP effectively reduced alcohol-induced oxidative damage by downregulating Keap1 protein levels in the liver, leading to increased expression of Nrf2 protein. The 16S rDNA sequencing results revealed that CP significantly restored the intestinal microbiota composition in ALD mice. These findings establish a strong association between gut microbiota and liver injury indicators, highlighting the potential of CP in preventing and treating ALD by modulating the gut-liver axis.

Ginsenoside Rk2, a dehydroprotopanaxadiol saponin, alleviates alcoholic liver disease via regulating NLRP3 and NLRP6 inflammasome signaling pathways in mice

Heavy alcohol consumption results in alcoholic liver disease (ALD) with inadequate therapeutic options. Here, we first report the potential beneficial effects of ginsenoside Rk2 (Rk2), a rare dehydroprotopanaxadiol saponin isolated from streamed ginseng, against alcoholic liver injury in mice. Chronic-plus-single-binge ethanol feeding caused severe liver injury, as manifested by significantly elevated serum aminotransferase levels, hepatic histological changes, increased lipid accumulation, oxidative stress, and inflammation in the liver. These deleterious effects were alleviated by the treatment with Rk2 (5 and 30 mg/kg). Acting as an nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inhibitor, Rk2 ameliorates alcohol-induced liver inflammation by inhibiting NLRP3 inflammasome signaling in the liver. Meanwhile, the treatment with Rk2 alleviated the alcohol-induced intestinal barrier dysfunction via enhancing NLRP6 inflammasome in the intestine. Our findings indicate that Rk2 is a promising agent for the prevention and treatment of ALD and other NLPR3-driven diseases.

Synergistic Protective Effect of Fermented Schizandrae Fructus Pomace and Hoveniae Semen cum Fructus Extracts Mixture in the Ethanol-Induced Hepatotoxicity

Schizandrae Fructus (SF), fruits of Schisandra chinensis (Turcz.) Baill. and Hoveniae Semen cum Fructus (HSCF), the dried peduncle of Hovenia dulcis Thunb., have long been used for alcohol detoxification in the traditional medicine of Korea and China. In the current study, we aimed to evaluate the potential synergistic hepatoprotective effect of a combination mixture (MSH) comprising fermented SF pomace (fSFP) and HSCF hot water extracts at a 1:1 (w:w) ratio against ethanol-induced liver toxicity. Subacute ethanol-mediated hepatotoxicity was induced by the oral administration of ethanol (5 g/kg) in C57BL/6J mice once daily for 14 consecutive days. One hour after each ethanol administration, MSH (50, 100, and 200 mg/kg) was also orally administered daily. MSH administration significantly reduced the serum activities of alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and γ-glutamyl transpeptidase. Histological observation indicated that MSH administration synergistically and significantly decreased the fatty changed region of hepatic parenchyma and the formation of lipid droplet in hepatocytes. Moreover, MSH significantly attenuated the hepatic triglyceride accumulation through reducing lipogenesis genes expression and increasing fatty acid oxidation genes expression. In addition, MSH significantly inhibited protein nitrosylation and lipid peroxidation by lowering cytochrome P450 2E1 enzyme activity and restoring the glutathione level, superoxide dismutase and catalase activity in liver. Furthermore, MSH synergistically decreased the mRNA level of tumor necrosis factor-α in the hepatic tissue. These findings indicate that MSH has potential for preventing alcoholic liver disease through inhibiting hepatic steatosis, oxidative stress, and inflammation.

An analysis of the nutritional effects of Schisandra chinensis components based on mass spectrometry technology

OBJECTIVE

Schisandra chinensis (Turcz.) Baill. (S. chinensis) is a Traditional Chinese medicinal herb that can be used both for medicinal purposes and as a food ingredient due to its beneficial properties, and it is enriched with a wide of natural plant nutrients, including flavonoids, phenolic acids, anthocyanins, lignans, triterpenes, organic acids, and sugars. At present, there is lack of comprehensive study or systemic characterization of nutritional and active ingredients of S. chinensis using innovative mass spectrometry techniques.

METHODS

The comprehensive review was conducted by searching the PubMed databases for relevant literature of various mass spectrometry techniques employed in the analysis of nutritional components in S. chinensis, as well as their main nutritional effects. The literature search covered the past 5 years until March 15, 2023.

RESULTS

The potential nutritional effects of S. chinensis are discussed, including its ability to enhance immunity, function as an antioxidant, anti-allergen, antidepressant, and anti-anxiety agent, as well as its ability to act as a sedative-hypnotic and improve memory, cognitive function, and metabolic imbalances. Meanwhile, the use of advanced mass spectrometry detection technologies have the potential to enable the discovery of new nutritional components of S. chinensis, and to verify the effects of different extraction methods on these components. The contents of anthocyanins, lignans, organic acids, and polysaccharides, the main nutritional components in S. chinensis, are also closely associated to its quality.

CONCLUSION

This review will provide guidelines for an in-depth study on the nutritional value of S. chinensis and for the development of healthy food products with effective components.

Label-Free Imaging Techniques to Evaluate Metabolic Changes Caused by Toxic Liver Injury in PCLS

Abuse with hepatotoxic agents is a major cause of acute liver failure. The search for new criteria indicating the acute or chronic pathological processes is still a challenging issue that requires the selection of effective tools and research models. Multiphoton microscopy with second harmonic generation (SHG) and fluorescence lifetime imaging microscopy (FLIM) are modern label-free methods of optical biomedical imaging for assessing the metabolic state of hepatocytes, therefore reflecting the functional state of the liver tissue. The aim of this work was to identify characteristic changes in the metabolic state of hepatocytes in precision-cut liver slices (PCLSs) under toxic damage by some of the most common toxins: ethanol, carbon tetrachloride (CCl4) and acetaminophen (APAP), commonly known as paracetamol. We have determined characteristic optical criteria for toxic liver damage, and these turn out to be specific for each toxic agent, reflecting the underlying pathological mechanisms of toxicity. The results obtained are consistent with standard methods of molecular and morphological analysis. Thus, our approach, based on optical biomedical imaging, is effective for intravital monitoring of the state of liver tissue in the case of toxic damage or even in cases of acute liver injury.

Spectrum-effect relationship study to reveal the pharmacodynamic substances in Flos Puerariae-Semen Hoveniae medicine pair for the treatment of alcohol-induced liver damage

ETHNOPHARMACOLOGICAL RELEVANCE

Alcoholic liver disease (ALD) is the most serious and irreversible liver damage associated with alcohol consumption. Flos Puerariae and Semen Hoveniae are traditional Chinese medicines (TCM) for dispelling the effects of alcohol. Many studies have shown that the combination of two medicinal materials has the enhanced effect of treating ALD.

AIM OF THE STUDY

The aim of this study is to assess the pharmacological effects of Flos Puerariae-Semen Hoveniae medicine pair, to elucidate its action mechanism in the treatment of alcohol-induced BRL-3A cells, and to reveal the active ingredients in the medicine pair that exerted pharmacological effects by spectrum-effect relationship study.

MATERIALS AND METHODS

Firstly, MTT assays, ELISA, fluorescence probe analysis, and Western blot were employed to study the underlying mechanisms of the medicine pair in alcohol-induced BRL-3A cells by examining pharmacodynamic indexes and related protein expression. Secondly, HPLC method was established for chemical chromatograms of the medicine pair with different ratios and the sample extracted by different solvents. Then, principal component analysis, pearson bivariate correlation analysis and grey relational analysis were applied for development of the spectrum-effect correlation between pharmacodynamic indexes and HPLC chromatograms. Moreover, prototype components and their metabolites in vivo were identified by the HPLC-MS method.

RESULTS

Flos Puerariae-Semen Hoveniae medicine pair remarkably increased cell viability, decreased the activity of ALT, AST, TC and TG, reduced the generation of TNF-α, IL-1β, IL-6, MDA and ROS, increased the activity of SOD and GSH-Px, reduced protein expression of CYP2E1, compared with alcohol-induced BRL-3A cells. The medicine pair modulated the PI3K/AKT/mTOR signaling pathways by up-regulating the levels of phospho-PI3K, phospho-AKT and phospho-mTOR. Also, the results of the spectrum-effect relationship study showed that P1 (chlorogenic acid), P3 (daidzin), P4 (6″-O-xylosyl-glycitin), P5 (glycitin), P6 (unknown), P7 (unknown), P9 (unknown), P10 (6″-O-xylosyl-tectoridin), P12 (tectoridin) and P23 (unknown) can be considered as the main components of the medicine pair in the treatment of ALD. Furthermore, 6″-O-xylosyl-tectoridin, tectoridin, daidzin, 6″-O-xylosyl-glycitin and glycitin can be absorbed into the blood and showed clear metabolic and excretion behaviors in rats.

CONCLUSION

In this study, the hepatoprotective effects and the pharmacology mechanism of Flos Puerariae-Semen Hoveniae medicine pair in alcohol-induced BRL-3A cells were initially investigated and revealed. Through the spectrum-effect relationship study, the potential pharmacodynamic constituents such as daidzin, 6″-O-xylosyl-glycitin, 6″-O-xylosyl-tectoridin, glycitin, and tectoridin exert pharmacological effects on alcohol-induced oxidative stress and inflammation by modulating the PI3K/AKT/mTOR signaling pathways. This study provided experimental basis and data support for revealing the pharmacodynamic substance basis and pharmacology mechanism in the treatment of ALD. Moreover, it provides a robust mean of exploring the primary effective components responsible for the bioactivity of complicated TCM.

Scutellarin prevents acute alcohol-induced liver injury via inhibiting oxidative stress by regulating the Nrf2/HO-1 pathway and inhibiting inflammation by regulating the AKT, p38 MAPK/NF-κB pathways

Alcoholic liver disease (ALD) is the most frequent liver disease worldwide, resulting in severe harm to personal health and posing a serious burden to public health. Based on the reported antioxidant and anti-inflammatory capacities of scutellarin (SCU), this study investigated its protective role in male BALB/c mice with acute alcoholic liver injury after oral administration (10, 25, and 50 mg/kg). The results indicated that SCU could lessen serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels and improve the histopathological changes in acute alcoholic liver; it reduced alcohol-induced malondialdehyde (MDA) content and increased glutathione peroxidase (GSH-Px), catalase (CAT), and superoxide dismutase (SOD) activity. Furthermore, SCU decreased tumor necrosis factor-‍α (TNF-‍α), interleukin-6 (IL-6), and IL-‍1β messenger RNA (mRNA) expression levels, weakened inducible nitric oxide synthase (iNOS) activity, and inhibited nucleotide-binding oligomerization domain (NOD)‍-like receptor protein 3 (NLRP3) inflammasome activation. Mechanistically, SCU suppressed cytochrome P450 family 2 subfamily E member 1 (CYP2E1) upregulation triggered by alcohol, increased the expression of oxidative stress-related nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) pathways, and suppressed the inflammation-related degradation of inhibitor of nuclear factor-‍κB (NF-‍κB)‍-‍α (IκBα) as well as activation of NF‍-‍κB by mediating the protein kinase B (AKT) and p38 mitogen-activated protein kinase (MAPK) pathways. These findings demonstrate that SCU protects against acute alcoholic liver injury via inhibiting oxidative stress by regulating the Nrf2/HO-1 pathway and suppressing inflammation by regulating the AKT, p38 MAPK/NF-κB pathways.

Red raspberry supplementation mitigates alcohol-induced liver injury associated with gut microbiota alteration and intestinal barrier dysfunction in mice

Alcoholic liver disease (ALD) is still a global health concern. Long-term alcohol intake alters the gut microbiota diversity and metabolic activity, and causes intestinal barrier dysfunction, leading to the development of ALD. This research explored the protective effects and underlying mechanisms of red raspberry (RR) on alcohol-related disorders in mice. Male C57BL/6J mice were fed a standard diet or a standard diet supplemented with 2%, 4%, and 8% weight/weight RR. Meanwhile, mice were administered 35% (v/v) ethanol (EtOH, 10 mL per kg body weight) intragastrically once daily for six weeks, except the control group mice. The results showed that RR supplementation decreased liver injury markers (alanine and aspartate transaminases) in the serum, reduced triglyceride level in the liver and downregulated hepatic cytochrome P450 2E1 mRNA expression in mice administered EtOH. In addition, EtOH-mediated oxidative stress in the liver was attenuated by RR supplementation through decreased hepatic malondialdehyde content and increased antioxidant (glutathione, glutathione peroxidase, and catalase) levels and activities in mice exposed to EtOH. Moreover, RR supplementation reversed EtOH-induced alteration in the cecal microbial composition at the phylum, order, genus, and species levels and improved the intestinal barrier function associated with the inhibition of the NF-κB/MLCK pathway, which was accompanied by upregulation of tight junctions (zonula occludens 1, occludin, claudin-1, and claudin-4) and E-cadherin mRNA and protein expressions. Accordingly, RR supplementation resulted in a decreased level of endotoxins in the serum and attenuation of the inflammatory response in the liver, illustrated by a significant decrease in tumor necrosis factor-alpha, interleukin (IL)-1β, and IL-6 levels. Overall, RR supplementation alleviated the adverse effects of chronic alcohol intake in C57BL/6J mice and could be a potential supplement for improving ALD.

Oenothein B ameliorates hepatic injury in alcoholic liver disease mice by improving oxidative stress and inflammation and modulating the gut microbiota

Introduction

Alcoholic liver disease (ALD) is a global health problem for which there is no current food and drug administration (FDA)-approved therapy. Oenothein B (OEB) is a macrocyclic dimer ellagic tannin that possesses abundant biological activities including antioxidant, anti-inflammation, antitumor, immunomodulatory, and antimicrobial properties.

Materials and methods

In this study, the hepatoprotective effect of OEB against ALD was investigated in vivo and in vitro.

Results

We found that OEB treatment dramatically reduced alcohol-induced hepatic injury, as evidenced by decreased levels of aminotransferases and inflammatory biomarkers and increased antioxidant capacity in OEB-treated groups.

Discussion

OEB treatment alleviated oxidative stress by upregulating the Keap1/Nrf2 signaling pathway and inhibited inflammation by downregulating the TLR4/NF-κB signaling pathway. Additionally, OEB treatment positively improved alcohol-induced intestinal microbial dysbiosis by modulating the structure and composition of gut microbiota. Interestingly, we observed the increasement of short-chain fatty acid (SCFA) producers (Muribaculaceae) and the decreasement of Gram-negative bacteria (Akkermansia) in the OEB treatment groups, which may contribute to the inhibition of hepatic oxidative stress and inflammation via the gut-liver axis. In summary, our findings indicate that OEB is a promising therapeutic strategy for preventing and treating ALD.

Association of promoter methylation status of NRF2 and PNPLA3 genes in alcoholic liver disease

BACKGROUND

Alcoholic liver disease (ALD) is the leading cause of chronic liver disease. In the liver, metabolism of alcohol occurs through multiple mechanisms and it results in the generation of various toxic products. Multiple genetic causes have been identified that are associated with the development and progression of ALD. The present study assessed the promoter site methylation status of nuclear factor erythroid 2-related factor 2 (NRF2) and patatin-like phospholipase domain-containing protein-3 (PNPLA3) genes in different subgroups of ALD.

METHODS

The patients recruited were cases of alcohol dependence syndrome with hepatic dysfunction, compensated cirrhosis, decompensated cirrhosis, and acute-on-chronic liver failure due to alcohol as an etiology along with healthy control subjects. Routine biochemical investigations were performed along with methylation-specific polymerase chain reaction (MS-PCR) to qualitatively assess the promoter methylation status of NRF2 and PNPLA3 in all these cases.

RESULTS

There was significant difference in methylation status of NRF2 gene in ALD when compared to healthy controls but there was no such difference in PNPLA3. All biochemical and clinical parameters studied were significantly different in subgroups of ALD except the serum aspartate aminotransferase (AST) level. Subgroups of ALD did not show any significant association with NRF2 or PNPLA3 methylation status. Gamma-glutamyl transferase (GGT) and creatinine levels in serum were significantly associated with the methylation status of NRF2 gene while no such association was seen with PNPLA3 gene. Model for end-stage liver disease (MELD) score varied differentially with NRF2 methylation and PNPLA3 methylation but there was no statistical significance.

CONCLUSIONS

The present study showed that methylation status of NRF2 and PNPLA3 genes could not differentiate between subgroups of alcoholic liver diseases. However, the unmethylation of NRF2 promoter is associated with higher serum levels of GGT.

Extracts of Dracocephalum tanguticum Maxim Ameliorate Acute Alcoholic Liver Disease via Regulating Transcription Factors in Mice

Alcoholic liver disease (ALD) caused by excessive drinking is a health and economic concern worldwide. Given the high morbidity, mortality, and the progressive nature of ALD, finding effective interventions is essential. Previous studies have confirmed that edible food plants and their bioactive compounds exert a protective effect against ALD. Dracocephalum tanguticum Maxim (DTM) is one of the important traditional Tibetan medicines in China with the effect of clearing away liver heat, used for the treatment of hepatitis. In this study, the DTM chloroform extract (DtM-C), ethyl acetate extract (DtM-E), and n-butanol extract (DtM-B) were obtained by ethanol extraction combined with fractional extraction. Acute ALD was induced in mice given intragastric ethanol. Serum and liver biochemical markers were detected by ELISA. Liver histological observation, Oil Red O, and Masson's trichrome staining were performed. Liver injury cells were induced by ethanol. The cell vitality was detected by using MTT colorimetry. The expressions of Nrf2, NF-κB, STAT3, AP-1, CREB, HIF-1α, HO-1, NQO-1, GSTA1, IKB2, and Keap1 were detected by real-time polymerase chain reaction (PCR) to elucidate the mechanism of hepatoprotective effect, and the results were verified by using Western blot. The results of serum liver function indicators (ALT, AST, and ADH), serum hepatic lipid indicators (TC, TG, HDL-C, and LDL-C), and lipid peroxidation indicators (ADH, MDA, SOD, CAT, and GSH-Px) in liver tissue and liver histological observation showed that DtM-E could improve liver function, alleviate fatty degeneration, edema, cell necrosis, and liver fibrosis caused by alcohol. DtM-E also increased the vitality of EtOH-induced liver injury cells, upregulated the mRNA expression of Nrf2, HO-1, NQO-1, and GSTA1, while downregulated the expression of Keap-1, p65, and NF-κB. Western blot results were consistent with PCR. The results suggest that DtM-E has a protective effect against ALD in vitro and in vivo, and its mechanism of action may be related to the activation of Nrf2/Keap-1 and inhibition of the P65/NF-κB signaling pathways.

Crosstalk between Oxidative Stress and Inflammatory Liver Injury in the Pathogenesis of Alcoholic Liver Disease

Alcoholic liver disease (ALD) is characterized by the injury, inflammation, and scarring in the liver owing to excessive alcohol consumption. Currently, ALD is a leading cause for liver transplantation. Therefore, extensive studies (in vitro, in experimental ALD models and in humans) are needed to elucidate pathological features and pathogenic mechanisms underlying ALD. Notably, oxidative changes in the liver have been recognized as a signature trait of ALD. Progression of ALD is linked to the generation of highly reactive free radicals by reactions involving ethanol and its metabolites. Furthermore, hepatic oxidative stress promotes tissue injury and, in turn, stimulates inflammatory responses in the liver, forming a pathological loop that promotes the progression of ALD. Accordingly, accumulating further knowledge on the relationship between oxidative stress and inflammation may help establish a viable therapeutic approach for treating ALD.

Echinacea purpurea polysaccharide prepared by fractional precipitation prevents alcoholic liver injury in mice by protecting the intestinal barrier and regulating liver-related pathways

Oxidative damage and intestinal dysbiosis are regarded as crucial culprits in alcoholic liver disease (ALD). This study aimed to examine the protective effects of Echinacea purpurea polysaccharides (EPPs) against ALD and explore the underlying mechanisms based on hepatic oxidative stress, inflammation, and intestinal barrier function. Three polysaccharide fractions, namely, EPP40, EPP60, and EPP80, were obtained by stepwise ethanol precipitation, and their antioxidant activity in vitro was investigated. The results showed that EPP80 with Mw 11.82 kDa had the strongest radical-scavenging capacity against DPPH, ABTS, and •OH radicals. Besides, EPP80 comprised arabinose, galactose, glucose, mannose, galacturonic acid, and glucuronic acid in molar ratios of 13.42:25.12:10.92:8.59:2.07:0.82. The in vivo results showed that EPP80 increased the activities of antioxidant enzymes and reduced the levels of inflammatory cytokines both in mouse serum and liver. Moreover, EPP80 upregulated the expression of Occludin and ZO-1, revealing its protective effect against intestinal barrier dysfunction. Furthermore, EPP80 inhibited alcohol-induced oxidative damage by promoting the expression of Nrf2, HO-1, and NQO1 in the liver. In summary, EPP80 markedly scavenged free radicals in vitro and ameliorated alcohol-induced liver injury via Nrf2/HO-1 pathways in vivo. These findings suggested that EPP80 could provide effective supplementary support in preventing and treating ALD.

Interplay between nuclear factor erythroid 2-related factor 2 and inflammatory mediators in COVID-19-related liver injury

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 is a global pandemic and poses a major threat to human health worldwide. In addition to respiratory symptoms, COVID-19 is usually accompanied by systemic inflammation and liver damage in moderate and severe cases. Nuclear factor erythroid 2-related factor 2 (NRF2) is a transcription factor that regulates the expression of antioxidant proteins, participating in COVID-19-mediated inflammation and liver injury. Here, we show the novel reciprocal regulation between NRF2 and inflammatory mediators associated with COVID-19-related liver injury. Additionally, we describe some mechanisms and treatment strategies.

Liver-specific Nrf2 deficiency accelerates ethanol-induced lethality and hepatic injury in vivo

Alcoholic liver disease (ALD) is a major cause of morbidity and mortality from liver disorders. Various mechanisms, including oxidative stress and impaired lipid metabolism, have been implicated in the pathogenesis of ALD. Our previous studies showed that nuclear factor erythroid-derived 2-like 2 (Nrf2) is a master regulator of adaptive antioxidant response and lipid metabolism by using a liver-specific Nrf2 knockout (Nrf2(L)-KO) mouse model. In the current study, an ALD model was developed by a Lieber-DeCarli liquid-based ethanol diet given to this Nrf2(L)-KO mouse strain. We found that Nrf2(L)-KO mice were quite sensitive to lethality from 6.3% ethanol diet. We thus decreased the ethanol concentration to 4.2% to obtain tissues to analyze the role of hepatic Nrf2 in the development of ALD. We found that mild hepatic steatosis occurred with both liquid control and 4.2% ethanol diet feeding, which contain 35% fat. Both the fatty acid β-oxidation marker peroxisome proliferators-activated receptor α (PPARα), and lipogenesis regulator PPARγ were reduced with ethanol feeding in Nrf2(L)-KO mice, compared to Nrf2 floxed control mice (Nrf2-LoxP). However, Nrf2(L)-KO livers showed more cell injury than the livers of Nrf2-LoxP mice. Consistent with these data, there was increased proportion of apoptotic cells in the liver of ethanol-fed Nrf2(L)-KO mice comparing Nrf2-LoxP controls. Mechanistically, Nrf2 mediated expression of ethanol detoxification enzymes, such as alcohol dehydrogenase 1 and aldehyde dehydrogenase1a1, likely contributed to the sensitivity to ethanol toxicity. In conclusion, hepatic Nrf2 is critical to the development of ALD, particularly the morbidity and liver injury.

Chronic Alcohol Exposure of Cells Using Controlled Alcohol-Releasing Capillaries

Alcohol is one of the main causes of liver diseases such as fatty liver, alcoholic hepatitis, and chronic hepatitis with liver fibrosis or cirrhosis. To reproduce the conditions of alcohol-induced liver diseases and to identify the disease-causing mechanisms at the cellular level, several methods have been used to expose the cells to ethanol. As ethanol evaporates easily, it is difficult to mimic chronic alcohol exposure conditions at the cellular level. In this study, we developed a glass capillary system containing ethanol, which could steadily release ethanol from the polyethylene tubing and hydrogel portion at both sides of the capillary. The ethanol-containing capillary could release ethanol in the cell culture medium for up to 144 h, and the concentration of ethanol in the cell culture medium could be adjusted by controlling the number of capillaries. A long-term exposure to ethanol by the capillary system led to an increased toxicity of cells and altered the cellular physiologies, such as increasing the lipid accumulation and hepatic transaminase release in cells, as compared to the traditional direct ethanol addition method. Ethanol capillaries showed different gene expression patterns of lipid accumulation- or chronic alcoholism-related genes. Our results suggest that our ethanol-containing capillary system can be used as a valuable tool for studying the mechanism of chronic alcohol-mediated hepatic diseases at the cellular level.

The protective effect of Veronica ciliata Fisch. Extracts on relieving oxidative stress-induced liver injury via activating AMPK/p62/Nrf2 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Veronica ciliata Fisch. existed in various Tibetan medicine prescriptions, which was recorded to treat liver diseases in the Tibetan medicine roll of Chinese materia medica.

HYPOTHESIS/PURPOSE

The current study aimed to examine the effect of active constituents from V.ciliata relieving oxidative stress-mediated liver injury and clarify the underlying mechanism.

MATERIALS AND METHODS

tert-Butyl hydroperoxide (BHP) induced liver injury in mice model was established to evaluate the hepatoprotective effect of ethyl acetate extract of V. ciliata (EAFVC). Serum and liver indicators, as well as the histopathological change of liver were examined. Next, the constituents of EAFVC were separated and characterized by high-speed countercurrent chromatography (HSCCC) and Ultra performance liquid chromatography-mass spectrometer (UPLC-MS), respectively. Based on the above, the antioxidant activity of EAFVC and two fractions was evaluated using 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2, 2'-azino-bis (3-ethylbenzothiazoli- ne-6-sulfonic acid) (ABTS) free radical scavenging assays. The hepatoprotective activity of EAFVC and its fractions/compounds attenuating ethanol-induced hepatocyte damage in BRL-3A cells was evaluated using the MTT method. The effect of the fraction and compounds with the strongest protective activity on ethanol-induced cytotoxicity, reactive oxygen species (ROS) accumulation, and glutathione (GSH) depletion was investigated. mRNA expression of nuclear factor-E2-related factor 2 (Nrf2) and nuclear factor of κB (NF-κB), as well as their downstream target genes, was determined by RT-qPCR. Finally, the potential mechanism of fraction 1 and luteolin on the AMPK/p62/Nrf2 signal pathway was studied using western blotting.

RESULTS

Firstly, EAFVC could relieve liver impairment induced by t-BHP in mice. Next, fraction 1 enriched with polyphenolic compounds and luteolin derived from EAFVC were screened to yield the highest hepatoprotective activity against ethanol-induced hepatocyte damage. Further study demonstrated that fraction 1 and luteolin relieved BRL-3A cells damage by decreasing the aspartate aminotransferase (AST), alanine transaminase (ALT) and lactate dehydrogenase (LDH) activities, ROS accumulation, as well as the depletion of GSH. Also, we determined that fraction 1 and luteolin suppressed inflammation and apoptosis of BRL-3A cells. The mechanistic studies indicated that fraction 1 could attenuate oxidative stress, inflammation, and apoptosis by activating AMPK phosphorylation, which promotes autophagy associated protein expression (LC3-B, Beclin1 and p62) as well as promote phosphorylation of p62 -dependent autophagic degradation of Keap1, to induce Nrf2 dissociation from Keap1 and translocate to nuclear. Nrf2 in the nuclear activate cytoprotective related genes to exert hepatoprotective function. Finally, we found that luteolin activated the protein expression of p-AMPK, p-p62, p62, Nrf2, and its downstream target genes.

CONCLUSIONS

This study clarified that fraction 1 enriched phenolic compounds could attenuate ethanol-induced liver injury in BRL-3A cells via activating AMPK/p62/Nrf2 pathway. Luteolin could serve as the major bioactive component in the therapeutic effect of fraction 1. These active constituents in V. ciliata could be used as the potential drugs targeted activation of AMPK or p62 for relieving oxidative stress-mediated liver disorders.

Metformin and Probiotics Interplay in Amelioration of Ethanol-Induced Oxidative Stress and Inflammatory Response in an In Vitro and In Vivo Model of Hepatic Injury

Alcohol-induced liver injury implicates inflammation and oxidative stress as important mediators. Despite rigorous research, there is still no Food and Drug Administration (FDA) approved therapies for any stage of alcoholic liver disease (ALD). Interestingly, metformin (Met) and several probiotic strains possess the potential of inhibiting alcoholic liver injury. Therefore, we investigated the effectiveness of combination therapy using a mixture of eight strains of lactic acid-producing bacteria, commercialized as Visbiome® (V) and Met in preventing the ethanol-induced hepatic injury using in vitro and in vivo models. Human HepG2 cells and male Wistar rats were exposed to ethanol and simultaneously treated with probiotic V or Met alone as well as in combination. Endoplasmic reticulum (ER) stress markers, inflammatory markers, lipid metabolism, reactive oxygen species (ROS) production, and oxidative stress were evaluated, using qRT-PCR, Oil red O staining, fluorimetry, and HPLC. In vitro, probiotic V and Met in combination prevented ethanol-induced cellular injury, ER stress, oxidative stress, and regulated lipid metabolism as well as inflammatory response in HepG2 cells. Probiotic V and Met also promoted macrophage polarization towards the M2 phenotype in ethanol-exposed RAW 264.7 macrophage cells. In vivo, combined administration of probiotic V and Met ameliorated the histopathological changes, inflammatory response, hepatic markers (liver enzymes), and lipid metabolism induced by ethanol. It also improved the antioxidant markers (HO-1 and Nrf-2), as seen by their protein levels in both HepG2 cells as well as liver tissue using ELISA. Hence, probiotic V may act, in addition to the Met, as an effective preventive treatment against ethanol-induced hepatic injury.

The three-spot seahorse-derived peptide PAGPRGPA attenuates ethanol-induced oxidative stress in LO2 cells through MAPKs, the Keap1/Nrf2 signalling pathway and amino acid metabolism

Alcoholic liver diseases (ALDs) impose a substantial health burden on many countries. Bioactive peptides isolated from people, marine organisms, animals and plants have shown hepatoprotective effects on animal and hepatocyte models. In this study, an LO2 cell model of ethanol-induced liver injury in vitro was constructed. We investigated the hepatoprotective effects of the three-spot seahorse bioactive peptide (SBP) PAGPRGPA (Pro-Ala-Gly-Pro-Arg-Gly-Pro-Ala; 721.39 Da) and characterised the underlying metabolic pathways and biomarkers through a nontargeted metabolomics approach. We found that ethanol-induced oxidative stress impaired the cellular antioxidant system, leading to an imbalance in cellular homeostasis. However, SBP with a certain antioxidant activity inhibited reactive oxygen species (ROS) production, excessive intracellular Ca2+ level and abnormal apoptosis. It also restored the superoxide dismutase (SOD) and glutathione (GSH) levels and attenuated ethanol-induced oxidative damage and inflammation. SBP suppressed the activation of mitogen-activated protein kinase (MAPK) in ethanol-stimulated LO2 cells. It also regulated the Kelch-like ECH-associated protein 1 (Keap1)/nuclear factor erythroid 2-related factor 2 (Nrf2) signalling pathway to protect LO2 cells from oxidative damage by promoting the expression of antioxidant enzymes, such as heme oxygenase-1 (HO-1). Furthermore, the metabolomics approach demonstrated nine different biomarkers and six metabolic pathways. In summary, the hepatoprotective mechanisms of SBP in vitro, which can be attributed to the upregulation of antioxidant substances and amino acid metabolism, attenuate ethanol-induced oxidative stress.

Phytochemical characterization and hepatoprotective effect of active fragment from Adhatoda vasica Nees. against tert-butyl hydroperoxide induced oxidative impairment via activating AMPK/p62/Nrf2 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Adhatoda vasica Nees., which existed in a large; number of Tibetan medicine prescriptions for hepatopathy, used as an adjuvant to treat liver diseases.

HYPOTHESIS/PURPOSE

Oxidative stress is the key player in the development and progression of liver pathogenesis. In recent years, research is increasingly being focused on exploitation of the active components from medicinal plants to combat the liver oxidative injury. In our study, we aimed to screen the active principles from A. vasica and clarify whether they could relieve oxidative damage induced by tert-Butyl hydroperoxide (t-BHP) and its potential mechanism via activating AMPK/p62/Nrf2 pathway.

MATERIALS AND METHODS

Ultra performance liquid chromatography (UPLC) was adopted for analysis of chemical composition in the extracts. Furthermore, the antioxidant activity of the fractions was evaluated using DPPH, ABTS and reducing power assay. Along with this, the compounds in this fraction with highest antioxidant activity were analyzed using UPLC-MS. Based on this, the condition for extracting flavonoids of this subfraction was optimized via response surface method. CCK-8 assay was used to detect cell viability. Detection kits were used to measure the activity changes of AST, ALT, LDH and CAT as well as MDA and GSH levels induced by t-BHP. Detection of reactive oxygen species (ROS) production was used DCFH-DA probe. DAPI staining and flow cytometry was used to detect cell apoptosis. In terms of the mechanistic studies, the expression of proteins involved in AMPK/p62/Nrf2 pathway was measured using western blotting.

RESULTS

Eventually, 70% ethanol extract from leaf of A. vasica was chosen due to its highest active components compared with other extracts. Further, ethyl acetate fraction derived from 70% ethanol extract in A. vasica (AVEA) possess highest ability for scavenging DPPH and ABTS free radicals as well as strongest reducing power than other fractions. Chemical composition analysis showed that AVEA contained 17 compounds, including 1 quinazoline alkaloid, 12 flavonoid-C-glycosides and 4 flavonoid-O-glycosides. In addition, the conditions (ratio of solid-liquid 1:14, the concentration of ethanol 73%, and the temperature 65 °C) were selected to enrich the flavonoids in AVEA. Furthermore, AVEA could attenuate t-BHP induced hepatocyte damage via increasing the cell viability, restoring abnormal the activities of AST, ALT, LDH and CAT as well as the levels of MDA and GSH. ROS fluorescence intensity was reduced by AVEA. Meanwhile, it could inhibit the cell apoptosis of BRL 3 A cells, as evidenced by restoration of cell morphology and decreasing the number of apoptotic cells. Further mechanistic studies indicated AVEA could promote p-AMPK expression to further induce autophagy adaptor-p62 protein expression, which could autophagic degradation of Keap1, leading to Nrf2 release and translocation into nucleus to induce antioxidant genes (HO-1, NQO-1, GCLC and GCLM) expression.

CONCLUSION

In our study, AVEA was first to screen as the active fraction in A. vasica with alkaloids and abundant flavones. Moreover, the fraction potentiates its beneficial aspect by displaying the protective role on relieving t-BHP induced oxidative stress and activating AMPK/p62/Nrf2 pathway. AVEA helps maintain the redox homeostasis of hepatic cells and could be considered as an effective candidate against oxidative stress related liver disorders.

Sulforaphane ameliorates ethanol plus carbon tetrachloride-induced liver fibrosis in mice through the Nrf2-mediated antioxidant response and acetaldehyde metabolization with inhibition of the LPS/TLR4 signaling pathway

Alcoholic liver disease (ALD)-related fibrosis results from a variety of mechanisms including the accumulation of acetaldehyde, reactive oxygen species, and hepatic overload of endogenous lipopolysaccharide (LPS). Alcohol cessation is the therapeutic mainstay for patients with all stages of ALD, whereas pharmacological strategies for liver fibrosis have not been established. Sulforaphane, a phytochemical found in cruciferous vegetables, activates nuclear factor erythroid 2-related factor 2 (Nrf2) and exerts anticancer, antidiabetic, and antimicrobial effects; however, few studies investigated its efficacy in the development of ALD-related fibrosis. Herein, we investigated the effect of sulforaphane on acetaldehyde metabolism and liver fibrosis in HepaRG and LX-2 cells, human hepatoma and hepatic stellate cell lines, respectively, as well as in a mouse model of alcoholic liver fibrosis induced by ethanol plus carbon tetrachloride (EtOH/CCl₄). Sulforaphane treatment induced the activity of acetaldehyde-metabolizing mitochondrial aldehyde dehydrogenase in HepaRG cells and suppressed the acetaldehyde-induced proliferation and profibrogenic activity in LX-2 cells with upregulation of Nrf2-regulated antioxidant genes, including HMOX1, NQO1, and GSTM3. Moreover, sulforaphane attenuated the LPS/toll-like receptor 4-mediated sensitization to transforming growth factor-β with downregulation of NADPH oxidase 1 (NOX1) and NOX4. In EtOH/CCl₄-treated mice, oral sulforaphane administration augmented hepatic acetaldehyde metabolism. Additionally, sulforaphane significantly inhibited Kupffer cell infiltration and fibrosis, decreased fat accumulation and lipid peroxidation, and induced Nrf2-regulated antioxidant response genes in EtOH/CCl₄-treated mice. Furthermore, sulforaphane treatment blunted hepatic exposure of gut-derived LPS and suppressed hepatic toll-like receptor 4 signaling pathway. Taken together, these results suggest sulforaphane as a novel therapeutic strategy in ALD-related liver fibrosis.

Alcoholic hepatitis and metabolic disturbance in female mice: a more tractable model than Nrf2-/- animals

Alcoholic hepatitis (AH) is the dramatic acute presentation of alcoholic liver disease, with a 15% mortality rate within 28 days in severe cases. Research into AH has been hampered by the lack of effective and reproducible murine models that can be operated under different regulatory frameworks internationally. The liquid Lieber-deCarli (LdC) diet has been used as a means of ad libitum delivery of alcohol but without any additional insult, and is associated with relatively mild liver injury. The transcription factor nuclear factor-erythroid 2-related factor 2 (Nrf2) protects against oxidative stress, and mice deficient in this molecule are suggested to be more sensitive to alcohol-induced injury. We have established a novel model of AH in mice and compared the nature of liver injury in C57/BL6 wild-type (WT) versus Nrf2-/- mice. Our data showed that both WT and Nrf2-/- mice demonstrate robust weight loss, and an increase in serum transaminase, steatosis and hepatic inflammation when exposed to diet and ethanol. This is accompanied by an increase in peripheral blood and hepatic myeloid cell populations, fibrogenic response and compensatory hepatocyte regeneration. We also noted characteristic disturbances in hepatic carbohydrate and lipid metabolism. Importantly, use of Nrf2-/- mice did not increase hepatic injury responses in our hands, and female WT mice exhibited a more-reproducible response. Thus, we have demonstrated that this simple murine model of AH can be used to induce an injury that recreates many of the key human features of AH - without the need for challenging surgical procedures to administer ethanol. This will be valuable for understanding of the pathogenesis of AH, for testing new therapeutic treatments or devising metabolic approaches to manage patients whilst in medical care.This article has an associated First Person interview with the joint first authors of the paper.

Hylocereus polyrhizus Peel Extract Retards Alcoholic Liver Disease Progression by Modulating Oxidative Stress and Inflammatory Responses in C57BL/6 Mice

Alcoholic liver disease (ALD) has become a health problem as alcohol consumption has increased annually. Hepatic lipid accumulation, oxidative stress, and inflammation are important factors in the progression of ALD. Red pitaya (Hylocereus polyrhizus (Weber) Britt. & Rose) peel is rich in polyphenols and betanins, which possess antioxidative and anti-inflammatory properties. Therefore, the aim of this study was to investigate the effects of red pitaya peel extract (PPE) on ALD and explore the associated mechanisms. C57BL/6 J mice were administered an ethanol liquid diet for 11 weeks with or without two different doses of PPE (500 and 1000 mg/kg BW). PPE treatment significantly ameliorated liver injury and hepatic fat accumulation, and it improved hepatic lipid metabolism via increases in AMPK and PPAR-α protein expression and a decrease in SREBP-1 expression. In addition, PPE inhibited CYP2E1 and Nrf2 protein expression, reduced endotoxin levels in the serum, and decreased TLR4 and MyD88 expression and inflammatory cytokine TNF-α and IL-1β levels in the liver. In conclusion, these findings suggest that PPE may prevent the progression of ALD by modulating lipid metabolism and reducing oxidative stress and inflammatory responses.

Molecular Mechanisms That Link Oxidative Stress, Inflammation, and Fibrosis in the Liver

Activated hepatic stellate cells (HSCs) and myofibroblasts are the main producers of extracellular matrix (ECM) proteins that form the fibrotic tissue that leads to hepatic fibrosis. Reactive oxygen species (ROS) can directly activate HSCs or induce inflammation or programmed cell death, especially pyroptosis, in hepatocytes, which in turn activates HSCs and fibroblasts to produce ECM proteins. Therefore, antioxidants and the nuclear factor E2-related factor-2 signaling pathway play critical roles in modulating the profibrogenic response. The master proinflammatory factors nuclear factor-κB (NF-κB) and the nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3) inflammasome may coordinate to produce and activate profibrogenic molecules such as interleukins 1β and 18, which effectively activate HSCs, to produce large amounts of fibrotic proteins. Furthermore, the NLRP3 inflammasome activates pro-caspase 1, which is upregulated by NF-κB, to produce caspase 1, which induces pyroptosis via gasdermin and the activation of HSCs. ROS play central roles in the activation of the NF-κB and NLRP3 signaling pathways via IκB (an inhibitor of NF-κB) and thioredoxin-interacting protein, respectively, thereby linking the molecular mechanisms of oxidative stress, inflammation and fibrosis. Elucidating these molecular pathways may pave the way for the development of therapeutic tools to interfere with specific targets.

Functional Food XingJiuTang Attenuates Alcohol-Induced Liver Injury by Regulating SIRT1/Nrf-2 Signaling Pathway

Lipid accumulation, inflammatory responses and oxidative stress have been implicated in the pathology of alcohol-induced liver injury (ALI). In this work, we evaluated the effects of the functional food XingJiuTang (XJT) on ALI and explored the underlying mechanism. We used alcohol-stimulated human normal hepatocytes L02 for in vitro experiments, while for in vivo experiments, 55 % alcohol was intragastrically administrated to C57BL/6 mice at 16 mL/kg with pre-administration of bifendate and XJT. Liver histology and function, along with the inflammatory cytokines, oxidative mediators and SIRT1/Nrf-2 pathway were evaluated. The results showed that XJT treatment significantly alleviated ALI, ameliorated lipid peroxidation, improved the liver function impaired by alcohol and inhibited the hepatocytes apoptosis in vitro and in vivo. In addition, XJT treatment modulated the activation of the SIRT1/Nrf-2 signaling pathway and suppressed the overexpression of NOX4. Overall, the functional food XJT effectively protects against experimental ALI via activating the SIRT1/Nrf-2 pathway.

Aqueous extract of Polygonatum sibiricum ameliorates ethanol-induced mice liver injury via regulation of the Nrf2/ARE pathway

This study investigates the hepatoprotective effect of the aqueous extract of Polygonatum sibiricum (AEPS) against ethanol-induced oxidative stress and explores underlying mechanisms. AEPS was administered by gavage to ICR mice for 30 days. The experimental mice were fed a 5% (v/v) ethanol on last 10 days and followed by a single megadose of ethanol (5 g/kg) to induce ethanol-induced liver injury. Pretreatment with AEPS significantly suppressed the ethanol-induced elevation of aminotransferase activities, total bilirubin (TBIL) level, triglyceride level, and alleviated liver histopathological lesions. Meanwhile, AEPS reduced the level of oxidative stress in the liver and significantly suppressed the mRNA levels of NOX1, p67phox, gp91phox, and CYP2E1. Additionally, AEPS significantly increased the mRNA and protein levels of Nrf2 and its downstream antioxidant genes and promoted the nuclear translocation of Nrf2 in mice liver. Therefore, AEPS can effectively reduce ethanol-induced liver injury via regulation of the Nrf2/ARE pathway. PRACTICAL APPLICATIONS: Alcohol abuse and alcoholism have become a serious public health problem worldwide. Since liver is the major organ of alcohol metabolism, the most impactful damage of alcohol occurs in the liver. Polygonatum sibiricum is a traditional Chinese galenical and it also can be used as food ingredients. Most studies have reported that polysaccharide, flavonoids and saponins are the main bioactive compounds in Polygonatum sibiricum which play important roles in anti-oxidation. AEPS is the aqueous extract of Polygonatum sibiricum and AEPS can protect the mice liver against ethanol-induced oxidative damage. Thus it can be potential antioxidants to product hepatoprotective food and the study also provides a theoretical basis for the development and application of food about Polygonatum sibiricum.

Nrf2 in Neoplastic and Non-Neoplastic Liver Diseases

Simple Summary

Although the Keap1-Nrf2 pathway represents a powerful cell defense mechanism against a variety of toxic insults, its role in acute or chronic liver damage and tumor development is not completely understood. This review addresses how Nrf2 is involved in liver pathophysiology and critically discusses the contrasting results emerging from the literature. The aim of the present report is to stimulate further investigation on the role of Nrf2 that could lead to define the best strategies to therapeutically target this pathway.

Abstract

Activation of the Keap1/Nrf2 pathway, the most important cell defense signal, triggered to neutralize the harmful effects of electrophilic and oxidative stress, plays a crucial role in cell survival. Therefore, its ability to attenuate acute and chronic liver damage, where oxidative stress represents the key player, is not surprising. On the other hand, while Nrf2 promotes proliferation in cancer cells, its role in non-neoplastic hepatocytes is a matter of debate. Another topic of uncertainty concerns the nature of the mechanisms of Nrf2 activation in hepatocarcinogenesis. Indeed, it remains unclear what is the main mechanism behind the sustained activation of the Keap1/Nrf2 pathway in hepatocarcinogenesis. This raises doubts about the best strategies to therapeutically target this pathway. In this review, we will analyze and discuss our present knowledge concerning the role of Nrf2 in hepatic physiology and pathology, including hepatocellular carcinoma. In particular, we will critically examine and discuss some findings originating from animal models that raise questions that still need to be adequately answered.

Hepatocyte-specific deficiency of Nrf2 exacerbates carbon tetrachloride-induced liver fibrosis via aggravated hepatocyte injury and subsequent inflammatory and fibrogenic responses

BACKGROUND

Liver fibrosis, in which hepatocyte damage and inflammatory response play critical roles, is a physiological response to chronic or iterative liver injury and can progress to cirrhosis over time. Nuclear factor E2-related factor 2 (Nrf2) is a master transcription factor that regulates oxidative and xenobiotic stress responses as well as inflammation.

METHOD

To ascertain the cell-specific roles of Nrf2 in hepatocytes and myeloid lineage cells in the progression of liver fibrosis, mice lacking Nrf2 specifically in hepatocytes [Nrf2(L)-KO] and myeloid lineage cells [Nrf2(M)-KO] were generated to evaluate carbon tetrachloride (CCl₄)-induced liver injury, subsequent inflammation and fibrosis. In addition, mouse primary hepatocytes were used to investigate the underlying mechanisms.

RESULTS

Nrf2-mediated antioxidant response in the liver is responsive to acute CCl₄ exposure in mice. With repeated CCl₄ administration, Nrf2(L)-KO, but not Nrf2(M)-KO, mice showed more severe liver fibrosis than Nrf2-LoxP control mice. In addition, in response to acute CCl₄ exposure, Nrf2(L)-KO mice displayed aggravated liver injury, elevated lipid peroxidation and inflammatory response compared to control mice. In mouse primary hepatocytes, deficiency of Nrf2 resulted in more severe CCl₄-induced lipid oxidation and inflammatory response.

CONCLUSION

Deficiency of Nrf2 in hepatocytes sensitizes the cells to CCl₄-induced oxidative damage and inflammatory response, which are initiator and enhancer of subsequent hepatic inflammation and fibrosis. Thus, Nrf2 is a critical determinant of liver injury and fibrosis in response to CCl₄, suggesting that Nrf2 might be a valuable target for the intervention.

A Novel Mouse Model of Acute-on-Chronic Cholestatic Alcoholic Liver Disease: A Systems Biology Comparison With Human Alcoholic Hepatitis

BACKGROUND

Alcohol-related liver disease is the main cause of liver-related mortality worldwide. The development of novel targeted therapies for patients with advanced forms (i.e., alcoholic hepatitis, AH) is hampered by the lack of suitable animal models. Here, we developed a novel mouse model of acute-on-chronic alcohol liver injury with cholestasis and fibrosis and performed an extensive molecular comparative analysis with human AH.

METHODS

For the mouse model of acute-on-chronic liver injury, we used 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC, 0.05% w/w) diet for 8 weeks to establish cholestatic liver fibrosis. After 1-week washout period, male mice were fed intragastrically for 4 weeks with up to 24 g/kg of ethyl alcohol in a high-fat diet. This animal model was phenotyped using histopathology, clinical chemistry, microbiome, and gene expression approaches. Data were compared to the phenotypes of human alcohol-related liver disease, including AH.

RESULTS

Mice with cholestatic liver fibrosis and subsequent alcohol exposure (DDC + EtOH) exhibited exacerbated liver fibrosis with a pericellular pattern, increased neutrophil infiltration, and ductular proliferation, all characteristics of human AH. DDC administration had no effect on urine alcohol concentration or liver steatosis. Importantly, DDC- and alcohol-treated mice showed a transcriptomic signature that resembled that of patients with AH. Finally, we show that mice in the DDC + EtOH group had an increased gut barrier dysfunction, mimicking an important pathophysiological mechanism of human AH.

CONCLUSIONS

We developed a novel mouse model of acute-on-chronic cholestatic alcoholic liver injury that has considerable translational potential and can be used to test novel therapeutic modalities for AH.

Free radicals, antioxidants, nuclear factor-E2-related factor-2 and liver damage

Oxidative/nitrosative stress is proposed to be a critical factor in various diseases, including liver pathologies. Antioxidants derived from medicinal plants have been studied extensively and are relevant to many illnesses, including liver diseases. Several hepatic disorders, such as viral hepatitis and alcoholic or nonalcoholic steatohepatitis, involve free radicals/oxidative stress as agents that cause or at least exacerbate liver injury, which can result in chronic liver diseases, such as liver fibrosis, cirrhosis and end-stage hepatocellular carcinoma. In this scenario, nuclear factor-E2-related factor-2 (Nrf2) appears to be an essential factor to counteract or attenuate oxidative or nitrosative stress in hepatic cells. In fact, a growing body of evidence indicates that Nrf2 plays complex and multicellular roles in hepatic inflammation, fibrosis, hepatocarcinogenesis and regeneration via the induction of its target genes. Inflammation is the most common feature of chronic liver diseases, triggering fibrosis, cirrhosis and hepatocellular carcinoma. Increasing evidence indicates that Nrf2 counteracts the proinflammatory process by modulating the recruitment of inflammatory cells and inducing the endogenous antioxidant response of the cell. In this review, the interactions between antioxidant and inflammatory molecular pathways are analyzed.

Mitochondrial Oxidative Stress and Antioxidants Balance in Fatty Liver Disease

Fatty liver disease is one of the most prevalent forms of chronic liver disease that encompasses both alcoholic liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD). Alcoholic steatohepatitis (ASH) and nonalcoholic steatohepatitis (NASH) are intermediate stages of ALD and NAFLD, which can progress to more advanced forms, including cirrhosis and hepatocellular carcinoma. Oxidative stress and particularly alterations in mitochondrial function are thought to play a significant role in both ASH and NASH and recognized to contribute to the generation of reactive oxygen species (ROS), as documented in experimental models. Despite the evidence of ROS generation, the therapeutic efficacy of treatment with antioxidants in patients with fatty liver disease has yielded poor results. Although oxidative stress is considered to be the disequilibrium between ROS and antioxidants, there is evidence that a subtle balance among antioxidants, particularly in mitochondria, is necessary to avoid the generation of ROS and hence oxidative stress. Conclusion: As mitochondria are a major source of ROS, the present review summarizes the role of mitochondrial oxidative stress in ASH and NASH and presents emerging data indicating the need to preserve mitochondrial antioxidant balance as a potential approach for the treatment of human fatty liver disease, which may pave the way for the design of future trials to test the therapeutic role of antioxidants in fatty liver disease.