Overexpression of manganese superoxide dismutase prevents alcohol-induced liver injury in the rat

Narirutin ameliorates alcohol-induced liver injury by targeting MAPK14 in zebrafish larvae

BACKGROUND

Alcohol-associated liver disease (ALD) encompasses a range of hepatic abnormalities, including isolated alcoholic steatosis, steatohepatitis, and cirrhosis. The flavanone-7-O-glycoside narirutin (NRT), the primary flavonoid in citrus peel, has antioxidant, anti-inflammatory, and lipid-lowering activity. We investigated the effects of NRT on liver injury induced by alcohol and explored the underlying mechanisms.

METHODS

Zebrafish larvae were used to investigate the effects of NRT on acute exposure to ethanol (EtOH). Liver phenotypic, morphological, and biochemical assessments were performed to evaluate the hepatoprotective effects of NRT. Network pharmacology and molecular docking analyses were conducted to identify candidate targets of NRT in EtOH-induced liver injury. A drug affinity responsive target stability (DARTS) assay was conducted to evaluate the binding of NRT to mitogen-activated protein kinase 14 (MAPK14). The mechanism of action of NRT was validated by reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) and Western blot analysis.

RESULTS

The liver phenotypic, morphological, and biochemical assessments revealed that NRT has potential therapeutic effects against acute EtOH-induced liver injury. RT-qPCR confirmed that NRT reversed the change in the expression of genes related to oxidative stress, lipogenesis, and the endoplasmic reticulum (ER)/unfolded protein response pathway. Network pharmacology and molecular docking analyses identified potential targets of NRT's protective effects and confirmed that NRT regulates the p38 MAPK signaling pathway by targeting mitogen-activated protein kinase 14 (MAPK14).

CONCLUSIONS

NRT mitigates alcohol-induced liver injury by preventing lipid formation, protecting the antioxidant system, and suppressing ER stress-induced apoptosis through MAPK14 modulation.

Mitochondrial Dysfunction: At the Nexus between Alcohol-Associated Immunometabolic Dysregulation and Tissue Injury

Alcohol misuse, directly or indirectly as a result of its metabolism, negatively impacts most tissues, including four with critical roles in energy metabolism regulation: the liver, pancreas, adipose, and skeletal muscle. Mitochondria have long been studied for their biosynthetic roles, such as ATP synthesis and initiation of apoptosis. However, current research has provided evidence that mitochondria participate in myriad cellular processes, including immune activation, nutrient sensing in pancreatic β-cells, and skeletal muscle stem and progenitor cell differentiation. The literature indicates that alcohol impairs mitochondrial respiratory capacity, promoting reactive oxygen species (ROS) generation and disrupting mitochondrial dynamics, leading to dysfunctional mitochondria accumulation. As discussed in this review, mitochondrial dyshomeostasis emerges at a nexus between alcohol-disrupted cellular energy metabolism and tissue injury. Here, we highlight this link and focus on alcohol-mediated disruption of immunometabolism, which refers to two distinct, yet interrelated processes. Extrinsic immunometabolism involves processes whereby immune cells and their products influence cellular and/or tissue metabolism. Intrinsic immunometabolism describes immune cell fuel utilization and bioenergetics that affect intracellular processes. Alcohol-induced mitochondrial dysregulation negatively impacts immunometabolism in immune cells, contributing to tissue injury. This review will present the current state of literature, describing alcohol-mediated metabolic and immunometabolic dysregulation from a mitochondrial perspective.

Insulin resistance enhances binge ethanol-induced liver injury through promoting oxidative stress and up-regulation CYP2E1

Alcoholic liver disease (ALD) has caused a serious burden on public and personal health in crowd with ethanol abuse. The effects of insulin resistance (IR) on ALD and the mechanisms underlying these responses are still not well understood. In this study, we investigated the changes of liver injury, inflammation, apoptosis, mitochondrial dysfunction and CYP2E1 changes in liver of mice exposed to ethanol with IR or not. We found IR increased the sensitivity of liver injury in mice exposed to ethanol, manifested as the increase serum activities of AST and ALT, the accumulation of triglycerides, the deterioration of liver pathology and increase of inflammatory factors. IR also exacerbated apoptosis and mitochondrial dysfunction in liver of mice exposed to ethanol. The increase of oxidative stress and the decrease of antioxidant defense ability might be responsible for the sensitizing effects of IR on ethanol-induced liver injury, supported by the increase of MDA levels and the decline of GSH/GSSG, the inactivation of antioxidant enzymes SOD, GR through the inhibition of Nrf-2 pathway. The activation of CYP2E1 might be also involved in the sensitizing effects of IR on ethanol induced liver injury in mice. These results demonstrated that IR exhibited a significant pro-oxidative and pro-apoptosis effects to aggravate alcoholic liver injury. Our study helped us to better understand the sensitive role of IR on ALD and suggested that alcohol intake may be more harmful for people with IR.

Hepatoprotective effects of sea cucumber ether-phospholipids against alcohol-induced lipid metabolic dysregulation and oxidative stress in mice

Sea cucumber is widely consumed as food and folk medicine in Asia, and its phospholipids are rich sources of dietary eicosapentaenoic acid enriched ether-phospholipids (ether-PLs). Emerging evidence suggests that ether-PLs are associated with neurodegenerative disease and steatohepatitis. However, the function and mechanism of ether-PLs in alcoholic liver disease (ALD) are not well understood. To this end, the present study sought to investigate the hepatoprotective effects of sea cucumber ether-PLs, including plasmenyl phosphatidylethanolamine (PlsEtn) and plasmanyl phosphatidylcholine (PlsCho), and their underlying mechanisms. Our results showed that compared with EtOH-induced mice, ether-PL treated mice showed improved liver histology, decreased serum ALT and AST levels, and reduced alcohol metabolic enzyme (ALDH2 and ADH1) expressions. Mechanistic studies showed that ether-PLs attenuated "first-hit" hepatic steatosis and lipid accumulation evoked by alcohol administration. Moreover, PlsEtn more effectively restored endogenous plasmalogen levels than PlsCho, thereby enhancing hepatic antioxidation against "second-hit" reactive oxygen species (ROS) due to the damaged mitochondria and abnormal ethanol metabolism. Taken together, sea cucumber ether-PLs show great potential to become a natural functional food against chronic alcohol-induced hepatic steatosis and lipid metabolic dysregulation.

Mitochondrial dysfunction and oxidative stress in liver of male albino rats after exposing to sub-chronic intoxication of chlorpyrifos, cypermethrin, and imidacloprid

The adverse effects of chlorpyrifos, cypermethrin, and imidacloprid on mitochondrial dysfunction and oxidative stress biomarkers were studied in rat liver. The liver deficiency was also confirmed by histological analysis and gel electrophoresis. Each insecticide was administered orally with five doses per week for 28 days to male albino rats at 1/50 of the LD₅₀ per insecticide. The results demonstrated that the mitochondrial dysfunction was confirmed by a significant decrease in NADH dehydrogenase and ATPase activities. Oxidative stress biomarkers include malondialdehyde (MDA), and protein carbonyl content (PCC) were significantly increased. However, superoxide dismutase (SOD) and glutathione S-transferase (GST) as antioxidant enzymes were significantly decreased in the mitochondria of the rat liver. HPLC analysis showed a significant increase of the 8-hydroxy-2'-deoxyguanosine (8-OH-2DG) as a biomarker of the DNA damage in rat liver. In addition, the residue levels of 0.96 and 0.29 μg/mL serum were found for cypermethrin and imidacloprid, respectively. However, chlorpyrifos not detected using the HPLC analysis. Blue native polyacrylamide gel electrophoresis (BN-PAGE) analysis showed a change in the pattern and sequence of complexions of the electron transport chain in liver mitochondria with treatment by such insecticides. The hepatic histological examination also showed symptoms of abnormalities after exposure to these insecticides.

SOD2 overexpression in bone marrow‑derived mesenchymal stem cells ameliorates hepatic ischemia/reperfusion injury

Hepatic ischemia/reperfusion injury (HIRI) is a complex pathophysiological process that may develop after liver transplantation and resection surgery, as well as in uncontrolled clinical conditions. Bone marrow‑derived mesenchymal stem cells (BM‑MSCs) are potential targets for liver diseases. Thus, the present study aimed to investigate the effects of superoxide dismutase 2 (SOD2) overexpression in BM‑MSCs on HIRI by constructing a HIRI rat model. The adenoviral vector containing SOD2 and the corresponding control vector were designed and constructed, and SOD2‑overexpressing BM‑MSCs were injected into the tail vein of the rats. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels, as well as pathological changes and the remnant liver regeneration rate were determined. The activities of SOD and glutathione peroxidase (GSH‑Px), and malondialdehyde (MDA) content were measured. Reactive oxygen species (ROS) were determined with 2',7'‑-dichlorofluorescein diacetate and measured via fluorescence microscopy. Cell apoptosis was assessed using TUNEL staining. Moreover, the expression levels of Bax, Bcl‑2 and caspase‑3 were detected via western blotting. SOD2‑overexpressing BM‑MSCs significantly reduced the elevation of serum AST and ALT levels. Furthermore, SOD2‑overexpressing BM‑MSCs enhanced SOD and GSH‑Px activities, and suppressed the production of MDA and ROS. Histopathological findings revealed that SOD2‑overexpressing BM‑MSCs decreased the number of TUNEL‑positive cells in the liver. It was also found that SOD2‑overexpressing BM‑MSCs promoted Bcl‑2 expression, but inhibited Bax and caspase‑3 expression in HIRI. Collectively, these findings suggest that SOD2‑overexpressing BM‑MSCs may provide therapeutic support in HIRI by inhibiting oxidative stress and hepatocyte apoptosis.

Fucoidan ameliorates acute and sub-chronic in vivo toxicity of the fungicide cholorothalonil in Oreochromis niloticus (Nile tilapia)

Fucoidans are sulfated glycans from marine algae that have both anti-cancer and anti-microbial properties. Chlorothalonil is a fungicide and insecticide commonly used in agriculture. Chlorothalonil is relatively toxic to fish and can potentially affect the aquaculture practices. In this study, we determined whether fucoidan administration would offer any protection from acute and subchronic toxicity of chlorothalonil on Nile tilapia. First, we tested the effect of chlorothalonil (20 to 140 μg/L, water-applied) on Nile tilapia in an acute exposure (six days). Survival analysis was performed, together with assessment of histopathology, oxidative stress (i.e., antioxidant status, hydrogen peroxide levels, malondialdehyde and nitric oxide levels) and immunohistochemistry to measure indicators of hepatic damage (i.e., caspase 3, p53, mini-chromosome maintenance proteins (MCM), and glutathione peroxidase). Chlorothalonil induced mild to severe histopathological alterations that were dose-dependent in various tissues of Nile tilapia. Chlorothalonil also induced oxidative stress as indicated by elevated biochemical markers. The highest recorded mortalities were associated with p53 expression. Additional feeding experiments were conducted with fucoidan (8 g/kg diet), following acute (40 μg/L for seven days) and sub-chronic (20 μg/L for six weeks) chlorothalonil application in Nile tilapia. Many of these same biochemical biomarkers of stress, oxidative damage response, and tissue pathology (evidence for hepatic neoplasm) were ameliorated by fucoidan, suggesting a protective effect of the compound. Agrochemicals are ubiquitous on a global scale, and the use of fucoidan as a feed additive may be beneficial for protecting aquatic animal health and aquaculture species from the impacts of chemical run-off.

Curcumin Can be Acts as Effective agent for Prevent or Treatment of Alcohol-induced Toxicity in Hepatocytes: An Illustrated Mechanistic Review

Previous studies have shown that alcohol abuse can cause serious liver damage and cirrhosis. The main pathway for these types of hepatocellular cell neurodegeneration is mitochondrial dysfunction, which causes lipid peroxidation and dysfunction of the glutathione ring and the defect of antioxidant enzymes in alcoholic hepatic cells. Alcohol can also initiate malicious inflammatory pathways and trigger the initiation and activation of intestinal and extrinsic apoptosis pathways in hepatocellular tissues that lead to cirrhosis. Previous studies have shown that curcumin may inhibit lipid peroxidation, glutathione dysfunction and restore antioxidant enzymes. Curcumin also modulates inflammation and the production of alcohol-induced biomarkers. Curcumin has been shown to play a critical role in the survival of alcoholic hepatocellular tissue. It has been shown that curcumin can induce and trigger mitochondrial biogenesis and, by this mechanism, prevent the occurrence of both intrinsic and extrinsic apoptosis pathways in liver cells that have been impaired by alcohol. According to this mechanism, curcumin may protect hepatocellular tissue from alcohol-induced cell degeneration and may therefore survive alcoholic hepatocellular tissue. . Based on these mechanisms, the protective functions of curcumin against alcohol-induced cell degeneration due to oxidative stress, inflammation, and apoptosis events in hepatocellular tissue have been recorded. Hence, in this research, we have attempted to evaluate and analyze the main contribution mechanism of curcumin cell defense properties against alcohol-induced hepatocellular damage, according to previous experimental and clinical studies, and in this way we report findings from major studies.

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.

β-Sitosterol attenuates liver injury in a rat model of chronic alcohol intake

Liver disease associated with long-term drinking is one of the leading causes of death. There is an urgent need for more effective drugs to reduce alcoholic liver damage. Yin Chen Hao, a traditional Chinese herbal medicine, is widely used for liver diseases. Here, we aimed to explore the protective effect of β-sitosterol (the active ingredient of Artemisia spp.) on alcoholic liver injuries. We treated the rats with alcohol and different dosages of β-sitosterol to detect the expression levels of liver function indicators in serum. The functions of β-sitosterol were evaluated based on variations in histology, liver function indicators and DNA oxidative damages. The underlying mechanism was investigated by measuring lipid peroxidation, the antioxidant, the expression of cytochrome P450 2E1 and the expression of apoptosis related genes. The results showed that β-sitosterol could improve liver histology and suppress biochemical indicators caused by alcohol in serum. In addition, β-sitosterol alleviates alcohol-induced oxidative stress, such as restoring erythrocyte membrane fluidity, reducing glutathione depletion, restoring antioxidant enzyme activity and reducing malondialdehyde overproduction. Furthermore, β-sitosterol downregulated the expression of apoptosis-related genes through the PI3K/Akt pathway. In conclusion, β-sitosterol has a protective effect on chronic alcoholism and has broad clinical application prospects in the treatment of alcohol-induced liver damage.

Riding the tiger - physiological and pathological effects of superoxide and hydrogen peroxide generated in the mitochondrial matrix

Elevated mitochondrial matrix superoxide and/or hydrogen peroxide concentrations drive a wide range of physiological responses and pathologies. Concentrations of superoxide and hydrogen peroxide in the mitochondrial matrix are set mainly by rates of production, the activities of superoxide dismutase-2 (SOD2) and peroxiredoxin-3 (PRDX3), and by diffusion of hydrogen peroxide to the cytosol. These considerations can be used to generate criteria for assessing whether changes in matrix superoxide or hydrogen peroxide are both necessary and sufficient to drive redox signaling and pathology: is a phenotype affected by suppressing superoxide and hydrogen peroxide production; by manipulating the levels of SOD2, PRDX3 or mitochondria-targeted catalase; and by adding mitochondria-targeted SOD/catalase mimetics or mitochondria-targeted antioxidants? Is the pathology associated with variants in SOD2 and PRDX3 genes? Filtering the large literature on mitochondrial redox signaling using these criteria highlights considerable evidence that mitochondrial superoxide and hydrogen peroxide drive physiological responses involved in cellular stress management, including apoptosis, autophagy, propagation of endoplasmic reticulum stress, cellular senescence, HIF1α signaling, and immune responses. They also affect cell proliferation, migration, differentiation, and the cell cycle. Filtering the huge literature on pathologies highlights strong experimental evidence that 30-40 pathologies may be driven by mitochondrial matrix superoxide or hydrogen peroxide. These can be grouped into overlapping and interacting categories: metabolic, cardiovascular, inflammatory, and neurological diseases; cancer; ischemia/reperfusion injury; aging and its diseases; external insults, and genetic diseases. Understanding the involvement of mitochondrial matrix superoxide and hydrogen peroxide concentrations in these diseases can facilitate the rational development of appropriate therapies.

Mitochondrial Glutathione: Recent Insights and Role in Disease

Mitochondria are the main source of reactive oxygen species (ROS), most of them deriving from the mitochondrial respiratory chain. Among the numerous enzymatic and non-enzymatic antioxidant systems present in mitochondria, mitochondrial glutathione (mGSH) emerges as the main line of defense for maintaining the appropriate mitochondrial redox environment. mGSH’s ability to act directly or as a co-factor in reactions catalyzed by other mitochondrial enzymes makes its presence essential to avoid or to repair oxidative modifications that can lead to mitochondrial dysfunction and subsequently to cell death. Since mitochondrial redox disorders play a central part in many diseases, harboring optimal levels of mGSH is vitally important. In this review, we will highlight the participation of mGSH as a contributor to disease progression in pathologies as diverse as Alzheimer’s disease, alcoholic and non-alcoholic steatohepatitis, or diabetic nephropathy. Furthermore, the involvement of mitochondrial ROS in the signaling of new prescribed drugs and in other pathologies (or in other unmet medical needs, such as gender differences or coronavirus disease of 2019 (COVID-19) treatment) is still being revealed; guaranteeing that research on mGSH will be an interesting topic for years to come.

Antioxidant Capacity-Related Preventive Effects of Shoumei (Slightly Fermented Camellia sinensis) Polyphenols against Hepatic Injury

Shoumei is a kind of white tea (slightly fermented Camellia sinensis) that is rich in polyphenols. In this study, polyphenols were extracted from Shoumei. High-performance liquid chromatography (HPLC) showed that the polyphenols included mainly gallic acid, catechin, hyperoside, and sulfuretin. In an in vitro experiment, H₂O₂ was used to induce oxidative damage in human normal hepatic L-02 cells. In an animal experiment, CCl₄ was used to induce liver injury. The in vitro results showed that Shoumei polyphenols inhibited oxidative damage in normal hepatic L-02 cells, and the in vivo results showed that the polyphenols effectively reduced liver index values in mice with liver injury. The polyphenols also decreased aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), triglyceride (TG), total cholesterol (TC), blood urea nitrogen (BUN), nitric oxide (NO), malondialdehyde (MDA), interleukin 6 (IL-6), interleukin 12 (IL-12), tumour necrosis factor alpha (TNF-α), and interferon gamma (IFN-γ) levels and increased albumin (ALB), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) levels in the serum of mice with liver injury. Furthermore, pathological observation showed that the Shoumei polyphenols reduced CCl₄-induced hepatocyte damage. qRT-PCR and Western blotting showed that the polyphenols upregulated the mRNA and protein expression of neuronal nitric oxide synthase (nNOS), endothelial nitric oxide synthase (eNOS), manganese- (Mn-) SOD, copper/zinc- (Cu/Zn-) SOD, CAT, and inhibitor of nuclear factor kappa B (NF-κB) alpha (IκB-α) and downregulated the expression of inducible nitric oxide synthase (iNOS) and NF-κB p65. The Shoumei polyphenols had a preventive effect against CCl₄-induced mouse liver injury equivalent to that of silymarin. The four polyphenols identified as the key substances responsible for this effect mediated the effect through their antioxidant capacity. These results suggest that Shoumei polyphenols are high-quality natural products with liver-protective effects.

Preventive effect of lemon seed flavonoids on carbon tetrachloride-induced liver injury in mice

The aim of this study was to determine the preventive effect of lemon seed flavonoids (LSF) on carbon tetrachloride-induced liver injury in mice. Liver injury was induced by injection with 2 mL kg-1 of carbon tetrachloride after administration of LSF by gavage. Liver index, serological parameters, and expression intensities of related mRNA and protein in the liver tissue were observed. The results indicated that LSF reduced liver weight and liver index, downregulated serum levels of AST, ALT, ALP, TG, TC, BUN, NO, and MDA, and upregulated levels of ALB, SOD, CAT, and GSH-Px in the mice with liver injury. It also downregulated serum cytokines, such as IL-6, IL-12, TNF-α, and IFN-γ in these mice. qPCR and western blot confirmed that LSF upregulated mRNA and protein expression of Mn-SOD, Cu/Zn-SOD, CAT, GSH-Px, and IκB-α, and downregulated expression of NF-κB-p65, iNOS, COX-2, TNF-α, IL-1β, and IL-6 in the liver tissue of mice with liver injury. The preventive effect on carbon tetrachloride-induced liver injury was attributed to (-)-epigallocatechin, caffeic acid, (-)-epicatechin, vitexin, quercetin, and hesperidin, which were active substances that were detected in LSF by HPLC. Moreover, the effect of LSF is similar to that of silymarin, but the synergistic effect of the five active substances working in concert acted to produce a more robust liver-protecting effect.

Dendrobium officinale polysaccharides protected against ethanol-induced acute liver injury in vivo and in vitro via the TLR4/NF-κB signaling pathway

Alcohol-induced liver injury is characterized by strong inflammation. Polysaccharides separated from herbs can prevent ethanol-induced liver injury. Dendrobium officinale Kimura et Migo leaves (D. officinale) are a new food resource that contains a certain amount of polysaccharide. However, the hepatoprotective effects and the potential mechanisms of D. officinale polysaccharide (DOP) remain unknown. Thus, this study aimed to assess the hepatoprotective effects and potential mechanism in vivo and in vitro of DOP. Male Sprague-Dawley rats were used to establish alcohol-induced liver injury models through the oral gavage of absolute alcohol (5 mL/kg) after the oral administration of DOP (400 and 100 mg/kg) for 30 days. Hematoxylin-eosin staining was used for the histological assessments of hepatocyte degeneration, and the AST and ALT levels in the serum and liver tissue were measured. The inflammatory markers were evaluated using ELISA and immunohistochemistry. The potential mechanism of DOP in alcohol-induced liver cell (LO2) injury in vitro was further identified. Results showed that DOP clearly decreased the AST in the serum and hepatic tissue, obviously reduced the production of inflammatory cytokines (such as IL-1β, IL-6, and TNF-α), and can successfully inhibit NF-κB phosphorylation in vivo. In vitro experiments indicated that DOP increased the LO2 cell viability; prevented LDH release prominently; reduced the secretion of IL-1β, IL-6, and TNF-α; and reversed the expression of IL-1β, IL-6, TNF-α, caspase 1, NLRP3, p-NF-κB, and TLR4. Overall, DOP can alleviate ethanol-induced acute liver injury via the TLR4/NF-κB signaling pathway.

Combination of Chronic Alcohol Consumption and High-Salt Intake Elicits Gut Microbial Alterations and Liver Steatosis in Mice

Alcohol is a globally well-established cause of fatty liver disease (FLD). Increased salt consumption is associated with an increased prevalence of adipocyte hypertrophy and liver injury. In this study, high dietary salt potentiated chronic alcohol-induced hepatic damage. We explored the physiological mechanism of alcoholic FLD in the gastrointestinal tract. Male C57BL/6J mice (8-week-old) were fed a high-salt diet (HSD; 4% NaCl) with or without chronic ethanol (CE) for 1 month. The fecal microbiota, serum biochemical indices, intestinal permeability, level of liver damage, and liver mitochondria were evaluated. The HSD, CE, and their combination (HSDE) significantly changed the gut microbiota's structure, and the HSDE mice contained more probiotic species (e.g., Bifidobacterium and Lactobacillus). The serum aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase levels were increased, and the lipid was accumulated in the liver tissues in the CE, HSD, and HSDE groups, which indicated liver damage, especially in the HSDE group. The increased intestinal permeability and mitochondrial dysfunction in the liver cells caused greater injury in the HSDE group than in the other groups. Thus, consuming HSD with alcohol contributes to FLD development and progression.

Isolation and Identification of Lactobacillus plantarum HFY05 from Natural Fermented Yak Yogurt and Its Effect on Alcoholic Liver Injury in Mice

Yak yogurt is a type of naturally fermented dairy product prepared by herdsmen in the Qinghai-Tibet Plateau, which is rich in microorganisms. In this study, a strain of Lactobacillus plantarum was isolated and identified from yak yogurt in Hongyuan, Sichuan Province and named Lactobacillus plantarum HFY05 (LP-HFY05). LP-HFY05 was compared with a common commercial strain of Lactobacillus delbrueckii subsp. bulgaricus (LDSB). LP-HFY05 showed better anti-artificial gastric acid and bile salt effects than LDSB in in vitro experiments, indicating its potential as a probiotic. In animal experiments, long-term alcohol gavage induced alcoholic liver injury. LP-HFY05 effectively reduced the liver index of mice with liver injury, downregulated the levels of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, triglyceride, total cholesterol, blood urea nitrogen, nitric oxide, and MDA and upregulated the levels of albumin, superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase in the serum of liver-injured mice. LP-HFY05 also reduced the levels of interleukin (IL)-6, IL-12, tumor necrosis factor-alpha, and interferon-gamma in the serum of liver-injured mice. The pathological observations showed that LP-HFY05 reduced the damage to liver cells caused by alcohol. Quantitative polymerase chain reaction and Western blot assays further showed that LP-HFY05 upregulated neuronal nitric oxide synthase, endothelial nitric oxide synthase, manganese-SOD, cuprozinc-SOD, CAT, and inhibitor of κB-α mRNA and protein expression and downregulated the expression of nuclear factor-κB-p65 and inducible nitric oxide synthase in the livers of liver-injured mice. A fecal analysis revealed that LP-HFY05 regulated the microbial content in the intestinal tract of mice with liver injury, increased the content of beneficial bacteria, including Bacteroides, Bifidobacterium, and Lactobacillus and reduced the content of harmful bacteria, including Firmicutes, Actinobacteria, Proteobacteria, and Enterobacteriaceae, thus, regulating intestinal microorganisms to protect against liver injury. The effect of LP-HFY05 on liver-injured mice was better than that of LDSB, and the effect was similar to that of silymarin. LP-HFY05 is a high-quality microbial strain with a liver protective effect on experimental mice with alcoholic liver injury.

White Peony (Fermented Camellia sinensis) Polyphenols Help Prevent Alcoholic Liver Injury via Antioxidation

White peony is a type of white tea (Camellia sinensis) rich in polyphenols. In this study, polyphenols were extracted from white peony. In vitro experiments showed that white peony polyphenols (WPPs) possess strong free radical scavenging capabilities toward 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). Long-term alcohol gavage was used to induce alcoholic liver injury in mice, and relevant indices of liver injury were examined. WPPs effectively reduced the liver indices of mice with liver injury. The serum levels of aspartate aminotransferase (ATS), alanine aminotransferase (ALT), alkaline phosphatase (ALP), triglycerides (TG), total cholesterol (TC), blood urea nitrogen (BUN), nitric oxide (NO), and malondialdehyde (MDA) were downregulated, while those of albumin (ALB), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) were upregulated. WPPs also reduced the serum levels of interluekin-6 (IL-6), interluekin-12 (IL-12), tumor necrosis factor-alpha (TNF-α), and interferon-gamma (IFN-γ) in mice with liver injury. Pathology results showed that WPPs reduced alcohol-induced liver cell damage. Quantitative polymerase chain reaction (qPCR) and western blot results revealed that WPPs upregulated the mRNA and protein expressions of neuronal nitric oxide synthase (nNOS), endothelial nitric oxide synthase (eNOS), manganese superoxide dismutase (Mn-SOD), cupro–zinc superoxide dismutase (Cu/Zn-SOD), and CAT and downregulated iNOS expression in the liver of mice with liver injury. WPPs protected against alcoholic liver injury, and this effect was equivalent to that of silymarin. High-performance liquid chromatography revealed that WPPs mainly contained the polyphenols gallic acid, catechinic acid, and hyperoside, which are critical for exerting preventive effects against alcoholic liver injury. Thus, WPPs are high-quality natural products with liver protective effects.

Natural compounds in the chemoprevention of alcoholic liver disease

Alcoholic liver disease (ALD), caused by excessive consumption of alcohol, is a major cause of chronic liver disease worldwide. Much effort has been expended to explore the pathogenesis of ALD. Hepatic cell injury, oxidative stress, inflammation, regeneration, and bacterial translocation are all involved in the pathogenesis of ALD. Immediate abstinence is the most important therapeutic treatment for affected individuals. However, the medical treatment for ALD had not advanced in a long period. Intriguingly, an increasing body of research indicates the potential of natural compounds in the targeted therapy of ALD. A plethora of dietary natural products such as flavonoids, resveratrol, saponins, and β-carotene are found to exert protective effects on ALD. This occurs through various mechanisms composed of antioxidative, anti-inflammatory, iron chelation, pro-apoptosis, and/or antiproliferation of hepatic stellate cells and hepatocellular carcinoma cells. In this review, we will summarize current knowledge about the pathogenesis and treatments of ALD and focus on the potential of natural compounds in ALD therapies and underlying mechanisms.

Chitinase-3-like-1 deficiency attenuates ethanol-induced liver injury by inhibition of sterol regulatory element binding protein 1-dependent triglyceride synthesis

OBJECTIVE

Alcohol overconsumption and abuse lead to alcoholic liver disease (ALD), which is a major chronic liver disease worldwide. Chitinase-3-like protein 1 (CHI3L1) have an important role in the pathogenesis of inflammatory disease. However, the role of CHI3L1 in ALD has not yet been reported. In the present study, we investigated the effect of CHI3L1 on chronic plus binge ethanol-induced liver injury.

METHODS

CHI3L1 knock out (KO) mice and their littermate control mice based on C57BL/6 (10-12 weeks old) were fed on a Lieber-DeCarli diet containing 6.6% ethanol for 10 days. And, CHI3L1 siRNA or CHI3L1 expressing vector was transfected HepG2 cells were treated with ethanol or without.

RESULTS

Ethanol-induced hepatic triglyceride (TG) levels and the mRNA levels of TG synthesis-related genes such as acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS) and stearoyl-CoA desaturase-1 (SCD1) were decreased in the liver of CHI3L1 knock out (KO) mice and the HepG2 cells transfected with CHI3L1 siRNA. Increased mRNA level and activation of SREBP1 which is transcription factor of ACC, FAS and SCD1 by ethanol feeding were reduced in the liver of ethanol-fed CHI3L1 KO mice. Moreover, ethanol-induced SREBP1 luciferase activity and mRNA level of SREBP1, ACC, FAS and SCD1 were also decreased in the HepG2 cells transfected with CHI3L1 siRNA, while those were further increased in the HepG2 cells treated with recombinant human CHI3L1. Furthermore, oxidative stress and up-regulated pro-inflammatory cytokines by ethanol were recovered in the liver of ethanol-fed CHI3L1 KO mice.

CONCLUSION

Our finding suggest that inhibition of CHI3L1 suppressed ethanol-induced liver injury through inhibition of TG synthesis, and the blocking of oxidative stress and hepatic inflammation induced SREBP1 activity could be significant.

Polycystic Ovarian Condition May Be a Risk Factor for Ovarian Tumor Development in the Laying Hen Model of Spontaneous Ovarian Cancer

Chronic inflammation and long-standing oxidative stress are potential predisposing factors for developing malignancies, including ovarian cancer (OVCA). Information on the association of ovarian chronic abnormal conditions, including polycystic ovarian syndrome (PCOS), with the development of OVCA is unknown. The goal of this study was to examine if polycystic ovarian conditions are associated with OVCA development. In the exploratory study, 3-4-year-old laying hens were randomly selected and examined for the presence of polycystic ovaries with cancer (PCOC). In the prospective study, hens were monitored by ultrasound scanning to detect the incidence of a polycystic ovaries and subsequent development of OVCA. Tissues from normal ovaries and PCOC were examined for macrophage infiltration, expression of interleukin-16, and superoxide dismutase 2. The exploratory study detected spontaneous PCOC at early and late stages in hens. PCOC in hens were accompanied with influx of macrophages (17.33 ± 2.26 in PCOC at the early stage and 24.24 ± 2.5 in PCOC at the late stage in 20 mm² areas of tissue as compared with 6.77 ± 1.58 in normal hens). Expression of interleukin-16 was more than 2.5-fold higher and superoxide dismutase 2 was approximately 3-fold higher in PCOC hens than normal hens. The prospective study showed the development of OVCA in some hens with polycystic ovarian condition (PCO). PCOC development in hens was associated with chronic inflammation in the ovary. Laying hens may represent a potential model for the study of spontaneous PCOS and its long-term risk of PCOC development.

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.

Lipid peroxidation derived reactive aldehydes in alcoholic liver disease

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

Targeting Nrf-2 is a promising intervention approach for the prevention of ethanol-induced liver disease

Alcoholic liver disease (ALD) remains to be a worldwide health problem. It is generally accepted that oxidative stress plays critical roles in the pathogenesis of ALD, and antioxidant therapy represents a logical strategy for the prevention and treatment of ALD. Nuclear factor erythroid-derived 2-like 2 (NFE2L2 or Nrf-2) is essential for the antioxidant responsive element (ARE)-mediated induction of endogenous antioxidant enzymes such as heme oxygenase 1 (HO-1) and glutamate-cysteine ligase [GCL, the rate-limiting enzyme in the synthesis of glutathione (GSH)]. Activation of Nrf-2 pathway by genetic manipulation or pharmacological agents has been demonstrated to provide protection against ALD, which suggests that targeting Nrf-2 may be a promising approach for the prevention and treatment of ALD. Herein, we review the relevant literature about the potential hepatoprotective roles of Nrf-2 activation against ALD.

Effect of Mixed Fruit and Vegetable Juice on Alcohol Hangovers in Healthy Adults

The purpose of this study was to investigate the effects of mixed fruit and vegetable juice on alcohol hangover in healthy adults in a randomized crossover trial. Angelica keiskei/green grape/pear juice (AGP juice) was a mixture of A. keiskei juice, green grape juice, and pear juice at 1:1:1 ratio. Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) activities of AGP juice were measured in vitro. Fifteen healthy adults consumed alcohol (1.25 g/kg weight), and either water (control group) or AGP juice (AGP juice group). Blood was collected and expiratory-air alcohol levels were measured at 0~360 min after drinking the alcohol. Compared with control, AGP juice had higher ADH and ALDH activity in vitro. The peak alcohol levels in expiratory-air and plasma after drinking AGP juice were significantly lower than those after drinking water. The area under the curves for expiratory-air and plasma alcohol of the AGP juice group were lower than those of the control group. Thirst and headache scores after intake of alcohol were significantly reduced by AGP juice consumption compared with the control group. These data demonstrated that AGP juice could contribute to eliminate alcohol toxicity and hangover symptoms by enhancing alcohol metabolizing enzyme activities.

Alcoholic Hepatitis: Lost in Translation

Alcoholic hepatitis is the most severe and acute form of alcoholic liver disease. The mortality rate associated with alcoholic hepatitis is high, largely due to the lack of suitable pharmacological interventions. While there has been substantial research in the area, generating pharmacological interventions has been plagued by the lack of a robust mouse model both for testing and for understanding the underlying pathology. A number of major notable advances have been made in this area recently, with the goal of generating a mouse model of alcoholic hepatitis. The purpose of this article is to review recent advances in modeling alcoholic liver disease both in vitro and in vivo in the mouse, and place them in the context of the greater spectrum of alcoholic liver disease, with a focus on how we can translate current advances into a high-fidelity model of alcoholic hepatitis. In addition, we will review the basic mechanisms of alcoholic hepatitis as it is currently understood, focusing on recent advancements in diagnosis, prognosis and current pathophysiology, especially as it relates to the profound immune dysfunction present during alcoholic hepatitis.

The role of human cytochrome P450 2E1 in liver inflammation and fibrosis

Cytochrome P450 2E1 (CYP2E1) plays an important role in alcohol and toxin metabolism by catalyzing the conversion of substrates into more polar metabolites and producing reactive oxygen species. Reactive oxygen species-induced oxidative stress promotes hepatocyte injury and death, which in turn induces inflammation, activation of hepatic stellate cells, and liver fibrosis. Here, we analyzed mice expressing only the human CYP2E1 gene (hCYP2E1) to determine differences in hCYP2E1 versus endogenous mouse Cyp2e1 function with different liver injuries. After intragastric alcohol feeding, CYP2E1 expression was induced in both hCYP2E1 and wild-type (Wt) mice. hCYP2E1 mice had greater inflammation, fibrosis, and lipid peroxidation but less hepatic steatosis. In addition, hCYP2E1 mice demonstrated increased expression of fibrogenic and proinflammatory genes but decreased expression of de novo lipogenic genes compared to Wt mice. Lipidomics of free fatty acid, triacylglycerol, diacylglycerol, and cholesterol ester species and proinflammatory prostaglandins support these conclusions. Carbon tetrachloride-induced injury suppressed expression of both mouse and human CYP2E1, but again hCYP2E1 mice exhibited greater hepatic stellate cell activation and fibrosis than Wt controls with comparable expression of proinflammatory genes. By contrast, 14-day bile duct ligation induced comparable cholestatic injury and fibrosis in both genotypes. Conclusion: Alcohol-induced liver fibrosis but not hepatic steatosis is more severe in the hCYP2E1 mouse than in the Wt mouse, demonstrating the use of this model to provide insight into the pathogenesis of alcoholic liver disease. (Hepatology Communications 2017;1:1043-1057).

Chronic Ethanol Metabolism Inhibits Hepatic Mitochondrial Superoxide Dismutase via Lysine Acetylation

BACKGROUND

Chronic ethanol (EtOH) consumption is a major cause of liver disease worldwide. Oxidative stress is a known consequence of EtOH metabolism and is thought to contribute significantly to alcoholic liver disease (ALD). Therefore, elucidating pathways leading to sustained oxidative stress and downstream redox imbalances may reveal how EtOH consumption leads to ALD. Recent studies suggest that EtOH metabolism impacts mitochondrial antioxidant processes through a number of proteomic alterations, including hyperacetylation of key antioxidant proteins.

METHODS

To elucidate mechanisms of EtOH-induced hepatic oxidative stress, we investigate a role for protein hyperacetylation in modulating mitochondrial superoxide dismutase (SOD2) structure and function in a 6-week Lieber-DeCarli murine model of EtOH consumption. Our experimental approach includes immunoblotting immunohistochemistry (IHC), activity assays, mass spectrometry, and in silico modeling.

RESULTS

We found that EtOH metabolism significantly increased the acetylation of SOD2 at 2 functionally relevant lysine sites, K68 and K122, resulting in a 40% decrease in enzyme activity while overall SOD2 abundance was unchanged. In vitro studies also reveal which lysine residues are more susceptible to acetylation. IHC analysis demonstrates that SOD2 hyperacetylation occurs near zone 3 within the liver, which is the main EtOH-metabolizing region of the liver.

CONCLUSIONS

Overall, the findings presented in this study support a role for EtOH-induced lysine acetylation as an adverse posttranslational modification within the mitochondria that directly impacts SOD2 charge state and activity. Last, the data presented here indicate that protein hyperacetylation may be a major factor contributing to an imbalance in hepatic redox homeostasis due to chronic EtOH metabolism.

Nrf2 modulates cell proliferation and antioxidants defenses during liver regeneration induced by partial hepatectomy

The objective was to determine the regulatory dynamic of Nrf2 during liver regeneration and the administration of EtOH and/or the G. schiedeanum extract. Male Wistar rats weighing 200-230 g were subjected to a 70% partial hepatectomy; they were then divided into three groups (groups 1-3). During the experiment, animals in Group 1 drank only water. The other two groups (2-3) received an intragastric dose of ethanol (1.5 g/kg BW, solution at 40% in isotonic saline solution). Additionally, rats in group 3 received a geranium extract daily at a dose of 300 mg/kg BW i.g. EtOh and/or Geranium schiedeanum was administered to rats with regenerating livers for 7 days. At the end of treatment, the activity was determined of the antioxidant enzymes, DNA concentration, TBARS, and TAC, in addition to the expression of Nrf-2, Cyclin D1, and Nqo1. EtOH increased ROS and Nrf-2, which activated the antioxidant defenses and delayed liver proliferation. On the other hand, Geranium schiedeanum exerted an antioxidant effect, diminishing ROS, but Nrf-2 expression increased, favoring liver proliferation through the increase of DNA concentration and the overexpression of Cyclin D1, however it did not activate the antioxidant defenses. In sum, it can be concluded that Nrf-2 possesses a regulatory dynamic that is evident in the presence of a toxic agent (EtOH) and/or a phytochemical agent with antioxidant capacity (Geranium schiedeanum) during liver regeneration.

Early-Phase Alcoholic Liver Disease: An Update on Animal Models, Pathology, and Pathogenesis

Alcoholic liver disease (ALD) remains to be one of the most common etiology of liver disease and is a major cause of morbidity and mortality worldwide. The pathologic stages of ALD comprises of steatosis, steatohepatitis, and fibrosis/cirrhosis. Steatosis and steatohepatitis represents the early phase of ALD and are precursor stages for fibrosis/cirrhosis. Numerous research efforts have been directed at recognizing cofactors interacting with alcohol in the pathogenesis of steatosis and steatohepatitis. This review will elucidate the constellation of complex pathogenesis, available animal models, and microscopic pathologic findings mostly in the early-phase of ALD. The role of endotoxin, reactive oxygen species, alcohol metabolism, and cytokines are discussed. Understanding the mechanisms of early-phase ALD should provide insight into the development of therapeutic strategies and thereby decrease the morbidity and mortality associated with ALD.

Mitochondrial generation of superoxide and hydrogen peroxide as the source of mitochondrial redox signaling

This review examines the generation of reactive oxygen species by mammalian mitochondria, and the status of different sites of production in redox signaling and pathology. Eleven distinct mitochondrial sites associated with substrate oxidation and oxidative phosphorylation leak electrons to oxygen to produce superoxide or hydrogen peroxide: oxoacid dehydrogenase complexes that feed electrons to NAD⁺; respiratory complexes I and III, and dehydrogenases, including complex II, that use ubiquinone as acceptor. The topologies, capacities, and substrate dependences of each site have recently clarified. Complex III and mitochondrial glycerol 3-phosphate dehydrogenase generate superoxide to the external side of the mitochondrial inner membrane as well as the matrix, the other sites generate superoxide and/or hydrogen peroxide exclusively in the matrix. These different site-specific topologies are important for redox signaling. The net rate of superoxide or hydrogen peroxide generation depends on the substrates present and the antioxidant systems active in the matrix and cytosol. The rate at each site can now be measured in complex substrate mixtures. In skeletal muscle mitochondria in media mimicking muscle cytosol at rest, four sites dominate, two in complex I and one each in complexes II and III. Specific suppressors of two sites have been identified, the outer ubiquinone-binding site in complex III (site III_Qo) and the site in complex I active during reverse electron transport (site I_Q). These suppressors prevent superoxide/hydrogen peroxide production from a specific site without affecting oxidative phosphorylation, making them excellent tools to investigate the status of the sites in redox signaling, and to suppress the sites to prevent pathologies. They allow the cellular roles of mitochondrial superoxide/hydrogen peroxide production to be investigated without catastrophic confounding bioenergetic effects. They show that sites III_Qo and I_Q are active in cells and have important roles in redox signaling (e.g. hypoxic signaling and ER-stress) and in causing oxidative damage in a variety of biological contexts.

Barley Sprouts Extract Attenuates Alcoholic Fatty Liver Injury in Mice by Reducing Inflammatory Response

It has been reported that barley leaves possess beneficial properties such as antioxidant, hypolipidemic, antidepressant, and antidiabetic. Interestingly, barley sprouts contain a high content of saponarin, which showed both anti-inflammatory and antioxidant activities. In this study, we evaluated the effect of barley sprouts on alcohol-induced liver injury mediated by inflammation and oxidative stress. Raw barley sprouts were extracted, and quantitative and qualitative analyses of its components were performed. The mice were fed a liquid alcohol diet with or without barley sprouts for four weeks. Lipopolysaccharide (LPS)-stimulated RAW 264.7 cells were used to study the effect of barley sprouts on inflammation. Alcohol intake for four weeks caused liver injury, evidenced by an increase in serum alanine aminotransferase and aspartate aminotransferase activities and tumor necrosis factor (TNF)-α levels. The accumulation of lipid in the liver was also significantly induced, whereas the glutathione (GSH) level was reduced. Moreover, the inflammation-related gene expression was dramatically increased. All these alcohol-induced changes were effectively prevented by barley sprouts treatment. In particular, pretreatment with barley sprouts significantly blocked inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 expression in LPS-stimulated RAW 264.7. This study suggests that the protective effect of barley sprouts against alcohol-induced liver injury is potentially attributable to its inhibition of the inflammatory response induced by alcohol.

Paradoxical Roles of Antioxidant Enzymes: Basic Mechanisms and Health Implications

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated from aerobic metabolism, as a result of accidental electron leakage as well as regulated enzymatic processes. Because ROS/RNS can induce oxidative injury and act in redox signaling, enzymes metabolizing them will inherently promote either health or disease, depending on the physiological context. It is thus misleading to consider conventionally called antioxidant enzymes to be largely, if not exclusively, health protective. Because such a notion is nonetheless common, we herein attempt to rationalize why this simplistic view should be avoided. First we give an updated summary of physiological phenotypes triggered in mouse models of overexpression or knockout of major antioxidant enzymes. Subsequently, we focus on a series of striking cases that demonstrate "paradoxical" outcomes, i.e., increased fitness upon deletion of antioxidant enzymes or disease triggered by their overexpression. We elaborate mechanisms by which these phenotypes are mediated via chemical, biological, and metabolic interactions of the antioxidant enzymes with their substrates, downstream events, and cellular context. Furthermore, we propose that novel treatments of antioxidant enzyme-related human diseases may be enabled by deliberate targeting of dual roles of the pertaining enzymes. We also discuss the potential of "antioxidant" nutrients and phytochemicals, via regulating the expression or function of antioxidant enzymes, in preventing, treating, or aggravating chronic diseases. We conclude that "paradoxical" roles of antioxidant enzymes in physiology, health, and disease derive from sophisticated molecular mechanisms of redox biology and metabolic homeostasis. Simply viewing antioxidant enzymes as always being beneficial is not only conceptually misleading but also clinically hazardous if such notions underpin medical treatment protocols based on modulation of redox pathways.

Hepatoprotective effect of licorice, the root of Glycyrrhiza uralensis Fischer, in alcohol-induced fatty liver disease

Background

Our previous study suggested that licorice has anti-inflammatory activity in lipopolysaccharide-stimulated microglial cells and anti-oxidative activity in tert-butyl hydroperoxide–induced oxidative liver damage. In this study, we evaluated the effect of licorice on chronic alcohol-induced fatty liver injury mediated by inflammation and oxidative stress.

Methods

Raw licorice was extracted, and quantitative and qualitative analysis of its components was performed by using LC–MS/MS. Mice were fed a liquid alcohol diet with or without licorice for 4 weeks.

Results

We have standardized 70 % fermented ethanol extracted licorice and confirmed by LC-MS/MS as glycyrrhizic acid (GA), 15.77 ± 0.34 μg/mg; liquiritin (LQ), 14.55 ± 0.42 μg/mg; and liquiritigenin (LG), 1.34 ± 0.02 μg/mg, respectively. Alcohol consumption increased serum alanine aminotransferase and aspartate aminotransferase activities and the levels of triglycerides and tumor necrosis factor (TNF)-α. Lipid accumulation in the liver was also markedly induced, whereas the glutathione level was reduced. All these alcohol-induced changes were effectively inhibited by licorice treatment. In particular, the hepatic glutathione level was restored and alcohol-induced TNF-α production was significantly inhibited by licorice.

Conclusion

Taken together, our data suggests that protective effect of licorice against alcohol-induced liver injury may be attributed to its anti-inflammatory activity and enhancement of antioxidant defense.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-016-0997-0) contains supplementary material, which is available to authorized users.

High Intrinsic Aerobic Capacity Protects against Ethanol-Induced Hepatic Injury and Metabolic Dysfunction: Study Using High Capacity Runner Rat Model

Rats artificially selected over several generations for high intrinsic endurance/aerobic capacity resulting in high capacity runners (HCR) has been developed to study the links between high aerobic fitness and protection from metabolic diseases (Wisloff et al., Science, 2005). We have previously shown that the HCR strain have elevated hepatic mitochondrial content and oxidative capacity. In this study, we tested if the elevated hepatic mitochondrial content in the HCR rat would provide "metabolic protection" from chronic ethanol-induced hepatic steatosis and injury. The Leiber-Decarli liquid diet with ethanol (7% v/v; HCR-E) and without (HCR-C) was given to HCR rats (n = 8 per group) from 14 to 20 weeks of age that were weight matched and pair-fed to assure isocaloric intake. Hepatic triglyceride (TG) content and macro- and microvesicular steatosis were significantly greater in HCR-E compared with HCR-C (p < 0.05). In addition, hepatic superoxide dismutase activity and glutathione levels were significantly (p < 0.05) reduced in the HCR-E rats. This hepatic phenotype also was associated with reduced total hepatic fatty acid oxidation (p = 0.03) and β-hydroxyacyl-CoA dehydrogenase activity (p = 0.01), and reductions in microsomal triglyceride transfer protein and apoB-100 protein content (p = 0.01) in HCR-E animals. However, despite these documented hepatic alterations, ethanol ingestion failed to induce significant hepatic liver injury, including no changes in hepatic inflammation, or serum alanine amino transferase (ALTs), free fatty acids (FFAs), triglycerides (TGs), insulin, or glucose. High intrinsic aerobic fitness did not reduce ethanol-induced hepatic steatosis, but protected against ethanol-induced hepatic injury and systemic metabolic dysfunction in a high aerobic capacity rat model.

Glycyrrhizin, silymarin, and ursodeoxycholic acid regulate a common hepatoprotective pathway in HepG2 cells

BACKGROUND

Glycyrrhizin, silymarin, and ursodeoxycholic acid are widely used hepatoprotectants for the treatment of liver disorders, such as hepatitis C virus infection, primary biliary cirrhosis, and hepatocellular carcinoma.

PURPOSE

The gene expression profiles of HepG2 cells responsive to glycyrrhizin, silymarin, and ursodeoxycholic acid were analyzed in this study.

METHODS

HepG2 cells were treated with 25 µM hepatoprotectants for 24 h. Gene expression profiles of hepatoprotectants-treated cells were analyzed by oligonucleotide microarray in triplicates. Nuclear factor-κB (NF-κB) activities were assessed by luciferase assay.

RESULTS

Among a total of 30,968 genes, 252 genes were commonly regulated by glycyrrhizin, silymarin, and ursodeoxycholic acid. These compounds affected the expression of genes relevant various biological pathways, such as neurotransmission, and glucose and lipid metabolism. Genes involved in hepatocarcinogenesis, apoptosis, and anti-oxidative pathways were differentially regulated by all compounds. Moreover, interaction networks showed that NF-κB might play a central role in the regulation of gene expression. Further analysis revealed that these hepatoprotectants inhibited NF-κB activities in a dose-dependent manner.

CONCLUSION

Our data suggested that glycyrrhizin, silymarin, and ursodeoxycholic acid regulated the expression of genes relevant to apoptosis and oxidative stress in HepG2 cells. Moreover, the regulation by these hepatoprotectants might be relevant to the suppression of NF-κB activities.

Hepatoprotective effect of Geranium schiedeanum against ethanol toxicity during liver regeneration

AIM: To evaluate the effect of an extract of Geranium schiedeanum (Gs) as a hepatoprotective agent against ethanol (EtOH)-induced toxicity in rats.

METHODS: Male Wistar rats weighing 200-230 g were subjected to a 70% partial hepatectomy (PH); they were then divided into three groups (groups 1-3). During the experiment, animals in group 1 drank only water. The other two groups (2-3) drank an aqueous solution of EtOH (40%, v/v). Additionally, rats in group 3 received a Gs extract daily at a dose of 300 mg/kg body weight intragastically. Subsequently, to identify markers of liver damage in serum, alanine aminotransferase, aspartate aminotransferase, albumin and bilirubin were measured by colorimetric methods. Glucose, triglyceride and cholesterol concentrations were also determined. In addition, oxidative damage was estimated by measuring lipid peroxidation [using thiobarbituric-acid reactive substances (TBARS)] in both plasma and the liver and by measuring the total concentration of antioxidants in serum and the total antioxidant capacity in the liver. In addition, a liver mass gain assessment, total DNA analysis and a morpho-histological analysis of the liver from animals in all three groups were performed and compared. Finally, the number of deaths observed in the three groups was analyzed.

RESULTS: Administration of the Geranium shiedeanum extract significantly reduced the unfavorable effect of ethanol on liver regeneration (restitution liver mass: PH-EtOH group 60.68% vs PH-Gs-EtOH group 69.22%). This finding was congruent with the reduced levels of hepatic enzymes and the sustained or increased levels of albumin and decreased bilirubin in serum. The extract also modified the metabolic processes that regulate glucose and lipid levels, as observed from the serum measurements. Lower antioxidant levels and the liver damage induced by EtOH administration appeared to be mitigated by the extract, as observed from the TBARs (PH-EtOH group 200.14 mmol/mg vs PH-Gs-EtOH group 54.20 mmol/mg; P < 0.05), total status of antioxidants (PH-EtOH group 1.43 mmol/L vs PH-Gs-EtOH group 1.99 mmol/L; P < 0.05), total antioxidant capacity values, liver mass gain and total DNA determination (PH-EtOH group 4.80 mg/g vs PH-Gs-EtOH 9.10 mg/g; P < 0.05). Overall, these processes could be related to decreased mortality in these treated animals.

CONCLUSION: The administered extract showed a hepatoprotective effect, limiting the EtOH-induced hepatotoxic effects. This effect can be related to modulating oxido-reduction processes.

Chronic ethanol consumption induces mitochondrial protein acetylation and oxidative stress in the kidney

In this study, we present the novel findings that chronic ethanol consumption induces mitochondrial protein hyperacetylation in the kidney and correlates with significantly increased renal oxidative stress. A major proteomic footprint of alcoholic liver disease (ALD) is an increase in hepatic mitochondrial protein acetylation. Protein hyperacetylation has been shown to alter enzymatic function of numerous proteins and plays a role in regulating metabolic processes. Renal mitochondrial targets of hyperacetylation include numerous metabolic and antioxidant pathways, such as lipid metabolism, oxidative phosphorylation, and amino acid metabolism, as well as glutathione and thioredoxin pathways. Disruption of protein lysine acetylation has the potential to impair renal function through metabolic dysregulation and decreased antioxidant capacity. Due to a significant elevation in ethanol-mediated renal oxidative stress, we highlight the acetylation of superoxide dismutase, peroxiredoxins, glutathione reductase, and glutathione transferase enzymes. Since oxidative stress is a known factor in ethanol-induced nephrotoxicity, we examined biochemical markers of protein hyperacetylation and oxidative stress. Our results demonstrate increased protein acetylation concurrent with depleted glutathione, altered Cys redox potential, and the presence of 4-HNE protein modifications in our 6-week model of early-stage alcoholic nephrotoxicity. These findings support the hypothesis that ethanol metabolism causes an influx of mitochondrial metabolic substrate, resulting in mitochondrial protein hyperacetylation with the potential to impact mitochondrial metabolic and antioxidant processes.

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Chronic ethanol metabolism induces mitochondrial protein hyperacetylation in the kidney.

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Ethanol-induced hyperacetylation occurs on metabolic and antioxidant proteins.

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The onset of renal oxidative stress correlates with mitochondrial protein hyperacetylation.

Alcoholic liver disease: mechanisms of injury and targeted treatment

Alcoholic liver disease (ALD) is a complex process that includes a wide spectrum of hepatic lesions, from steatosis to cirrhosis. Cell injury, inflammation, oxidative stress, regeneration and bacterial translocation are key drivers of alcohol-induced liver injury. Alcoholic hepatitis is the most severe form of all the alcohol-induced liver lesions. Animal models of ALD mainly involve mild liver damage (that is, steatosis and moderate inflammation), whereas severe alcoholic hepatitis in humans occurs in the setting of cirrhosis and is associated with severe liver failure. For this reason, translational studies using humans and human samples are crucial for the development of new therapeutic strategies. Although multiple attempts have been made to improve patient outcome, the treatment of alcoholic hepatitis is still based on abstinence from alcohol and brief exposure to corticosteroids. However, nearly 40% of patients with the most severe forms of alcoholic hepatitis will not benefit from treatment. We suggest that future clinical trials need to focus on end points other than mortality. This Review discusses the main pathways associated with the progression of liver disease, as well as potential therapeutic strategies targeting these pathways.

Mitochondrial cholesterol accumulation in alcoholic liver disease: Role of ASMase and endoplasmic reticulum stress

Alcoholic liver disease (ALD) is a major cause of chronic liver disease and a growing health concern in theworld. While the pathogenesis of ALD is poorly characterized key players identified in experimental models and patients, such as perturbations in mitochondrial structure and function, selective loss of antioxidant defense and susceptibility to inflammatory cytokines, contribute to ALD progression. Both oxidative stress and mitochondrial dysfunction compromise essential cellular functions and energy generation and hence are important pathogenic mechanisms of ALD. An important process mediating the mitochondrial disruption induced by alcohol intake is the trafficking of cholesterol to mitochondria, mediated by acid sphingomyelinase-induced endoplasmic reticulum stress, which contributes to increased cholesterol synthesis and StARD1upregulation. Mitochondrial cholesterol accumulation not only sensitizes to oxidative stress but it can contribute to the metabolic reprogramming in ALD, manifested by activation of the hypoxia inducible transcription factor 1 and stimulation of glycolysis and lactate secretion. Thus, a better understanding of the mechanisms underlying alcohol-mediated mitochondrial impairment and oxidative stress may lead to the identification of novel treatments for ALD. The present review briefly summarizes current knowledge on the cellular and molecular mechanisms contributing to alcohol-induced mitochondrial dysfunction and cholesterol accumulation and provides insights for potential therapeutic targets in ALD.

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Alcohol perturbs mitochondria function, which modulates ROS generation and alcohol metabolism.

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Alcohol stimulates mitochondrial cholesterol (mChol) accumulation.

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MChol accumulation impairs mitochondrial function and mediates alcohol-induced lipotoxicity.

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ASMase promotes mitochondrial dysfunction by stimulating mChol loading.

Oleanolic acid co-administration alleviates ethanol-induced hepatic injury via Nrf-2 and ethanol-metabolizing modulating in rats

Alcoholic liver disease (ALD) is one of the leading causes of death in the world. Oxidative stress plays an important role in the pathogenesis of alcohol-induced liver injury. Our previous results have found that oleanolic acid (OA), a liver protective agent, plays a potent antioxidant activity in hepatocyte. In the present study, the protective effects of OA co-administration on ethanol-induced oxidative injury in rats were investigated through detecting hepatic histopathology, antioxidant enzymes, ethanol metabolic enzymes and inflammatory factors. Preventions of ethanol-induced oxidative injury by OA were reflected by markedly decreased serum activities of AST, ALT and significantly increased the hepatic ATP level. In addition, the increase of the hepatic TG content, MDA level and the decrease of hepatic GSH level, SOD activity, CAT activity induced by ethanol were significantly inhibited by OA co-administration. Furthermore, OA could also elevate the protein expressions and nuclear translocation of antioxidant transcription factor Nrf-2 and then up-regulated antioxidant enzymes expressions of HO-1, SOD-1 and GR. Moreover, OA co-administration can significantly reduce the activity and expressions of CYP2E1 and ADH, which has characteristic of generation ROS mediated oxidative stress and acetaldehyde respectively. Furthermore, OA co-administration could inhibition of the generation of inflammatory factors TNF-α and IL-6. Those above results indicated that OA co-administration can protect rats against ethanol-induced liver injury by induction Nrf-2 related antioxidant to maintain redox balance and modulating the ethanol-metabolizing and inflammatory pathway.

Alcohol stress, membranes, and chaperones

Ethanol, which affects all body organs, exerts a number of cytotoxic effects, most of them independent of cell type. Ethanol treatment leads to increased membrane fluidity and to changes in membrane protein composition. It can also interact directly with membrane proteins, causing conformational changes and thereby influencing their function. The cytotoxic action may include an increased level of oxidative stress. Heat shock protein molecular chaperones are ubiquitously expressed evolutionarily conserved proteins which serve as critical regulators of cellular homeostasis. Heat shock proteins can be induced by various forms of stresses such as elevated temperature, alcohol treatment, or ischemia, and they are also upregulated in certain pathological conditions. As heat shock and ethanol stress provoke similar responses, it is likely that heat shock protein activation also has a role in the protection of membranes and other cellular components during alcohol stress.

Prophylactic effect of aqueous extract of Sesamum indicum seeds on ethanol-induced toxicity in male rats

The liver is vulnerable to alcohol-related injury because it is the primary site of alcohol metabolism. Additionally, a number of potentially dangerous by-products are generated as alcohol is broken down in the liver. However, dietary supplements may prevent or relieve some of alcohol's deleterious effects. Therefore, this study was conducted to evaluate the prophylactic effect of aqueous extract of Sesamum indicum (SI) on ethanol induced toxicity in rats. Male Wistar albino rats were divided into control, ethanol, pre-treatment, simultaneous and post-treatment groups. In the prophylactic experiment, Sesamum indicum, (200 mg/kg body weight) was administered by oral gavage for 28 days; two hours before, simultaneously with or two hours after ethanol exposure. Toxicity was induced by administering 45% ethanol (4.8 g/kg bw) by oral gavage. Lipid peroxidation (TBARS) and reduced glutathione (GSH) levels and catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD) and gluthathione-S-transferase (GST) activities were then determined in the liver, serum triglyceride (TG) levels, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities were monitored and histological examination was carried out. The results revealed that ethanol administration led to significant elevation of TBARS level while depleting in the level of GSH as well as CAT, GPx, SOD and GST activities. Similarly, TG level and ALT and AST activities were elevated. The SI pre-treated group significantly inhibited TBARS, restored GSH level, enhanced CAT, GPx, SOD and GST activities and significantly decreased the elevated level of serum TG, ALT and AST activities. SI treatment (simultaneously with ethanol) exhibited similar effects to those of the SI pre-treated groups, while the SI post-treated group did not show the same protection as the Pre-treated group. S. indicum possesses antioxidant and hepatoprotective properties, that eliminate the deleterious effects of toxic metabolites of ethanol.

Sulforaphane induces Nrf2 and protects against CYP2E1-dependent binge alcohol-induced liver steatosis

BACKGROUND

The mechanism(s) by which alcohol causes cell injury are still not clear but a major mechanism appears to be the role of lipid peroxidation and oxidative stress in alcohol toxicity. CYP2E1-generated ROS contributes to the ethanol-induced oxidant stress and inhibition of CYP2E1 activity decreases ethanol-induced fatty liver. The transcription factor Nrf2 regulates the expression of many cytoprotective enzymes which results in cellular protection against a variety of toxins.

METHOD

The current study was designed to evaluate the ability of sulforaphane, an activator of Nrf2, to blunt CYP2E1-dependent, ethanol-induced steatosis in vivo and in vitro.

RESULTS

The sulforaphane treatment activated Nrf2, increased levels of the Nrf2 target heme oxygenase-1 and subsequently lowered oxidant stress as shown by the decline in lipid peroxidation and 3-nitrotyrosine protein adducts and an increase in GSH levels after the acute ethanol treatment. It decreased ethanol-elevated liver levels of triglycerides and cholesterol and Oil Red O staining. Similar results were found in vitro as addition of sulforaphane to HepG2 E47 cells, which express CYP2E1, elevated Nrf2 levels and decreased the accumulation of lipid in cells cultured with ethanol. Sulforaphane treatment had no effect on levels of or activity of CYP2E1.

CONCLUSIONS

Sulforaphane proved to be an effective in vivo inhibitor of acute ethanol-induced fatty liver in mice.

GENERAL SIGNIFICANCE

The possible amelioration of liver injury which occurs under these conditions by chemical activators of Nrf2 is of clinical relevance and worthy of further study.

Hepatitis C and alcohol exacerbate liver injury by suppression of FOXO3

Hepatitis C virus (HCV) infection exacerbates alcoholic liver injury by mechanisms that include enhanced oxidative stress. The forkhead box transcription factor FOXO3 is an important component of the antioxidant stress response that can be altered by HCV. To test whether FOXO3 is protective for alcoholic liver injury, we fed alcohol to FOXO3(-/-) mice. After 3 weeks, one third of these mice developed severe hepatic steatosis, neutrophilic infiltration, and >10-fold alanine aminotransferase (ALT) elevations. In cell culture, either alcohol or HCV infection alone increased FOXO3 transcriptional activity and expression of target genes, but the combination of HCV and alcohol together caused loss of nuclear FOXO3 and decreased its transcriptional activity. This was accompanied by increased phosphorylation of FOXO3. Mice expressing HCV structural proteins on a background of reduced expression of superoxide dismutase 2 (SOD2; Sod2(+/-)) also had increased liver sensitivity to alcohol, with elevated ALT, steatosis, and lobular inflammation. Elevated ALT was associated with an alcohol-induced decrease in SOD2 and redistribution of FOXO3 to the cytosol. These results demonstrate that FOXO3 functions as a protective factor preventing alcoholic liver injury. The combination of HCV and alcohol, but not either condition alone, inactivates FOXO3, causing a decrease in expression of its target genes and an increase in liver injury. Modulation of the FOXO3 pathway is a potential therapeutic approach for HCV-alcohol-induced liver injury.