Role of free radicals in liver diseases

Protective Effect of Caffeic Acid Derivatives on tert-Butyl Hydroperoxide-Induced Oxidative Hepato-Toxicity and Mitochondrial Dysfunction in HepG2 Cells

Oxidative stress results in structural and functional abnormalities in the liver and is thought to be a crucial factor in liver diseases. The aim of this study was to investigate the cytoprotective and antioxidant effects of caffeic acid (CA) derivatives on tert-butyl hydroperoxide (t-BHP)-induced oxidative stress in HepG2 cells. Nine CA derivatives were synthesized, including N-phenylethyl caffeamide (PECA), N-(3-florophen)methyl caffeamide (FMCA), N-(4-methoxy-phen)methyl caffeamide (MPMCA), N-heptyl caffeamide (HCA), N-octyl caffeamide (OCA), octyl caffeate (CAOE), phenpropyl caffeate (CAPPE), phenethyl caffeate (CAPE), and phenmethyl caffeate (CAPME). The results showed that CA and its derivatives significantly inhibited t-BHP-induced cell death of HepG2 cells. The rank order of potency of the CA derivatives for cytoprotection was CAOE > HCA > OCA > FMCA > CAPPE > CAPME > CAPE > PECA > MPMCA > CA. Their cytoprotective activity was associated with lipophilicity. The antioxidant effect of these compounds was supported by the reduction in the levels of thiobarbituric acid reactive substrates, a biomarker of lipid peroxidation, in HepG2 cells. Pre-treatment of CA derivatives significantly prevented the depletion of glutathione, the most important water-soluble antioxidant in hepatocytes. Pre-treatment of CA derivatives before t-BHP exposure maintained mitochondrial oxygen consumption rate and ATP content in the injured HepG2 cells. CA derivatives except OCA and HCA significantly suppressed t-BHP-induced hypoxia-inducible factor-1α (HIF-1α) protein level. In addition, all of these CA derivatives markedly increased the nuclear factor erythroid 2-related factor 2 (Nrf2) accumulation in the nucleus, indicating that their cytoprotection may be mediated by the activation of Nrf2. Our results suggest that CA derivatives might be a hepatoprotective agent against oxidative stress.

Reversal of liver fibrosis: From fiction to reality

In chronic liver diseases, an ongoing hepatocellular injury together with inflammatory reaction results in activation of hepatic stellate cells (HSCs) and increased deposition of extracellular matrix (ECM) termed as liver fibrosis. It can progress to cirrhosis that is characterized by parenchymal and vascular architectural changes together with the presence of regenerative nodules. Even at late stage, liver fibrosis is reversible and the underlying mechanisms include a switch in the inflammatory environment, elimination or regression of activated HSCs and degradation of ECM. While animal models have been indispensable for our understanding of liver fibrosis, they possess several important limitations and need to be further refined. A better insight into the liver fibrogenesis resulted in a large number of clinical trials aiming at reversing liver fibrosis, particularly in patients with non-alcoholic steatohepatitis. Collectively, the current developments demonstrate that reversal of liver fibrosis is turning from fiction to reality.

Vegetable and fruit juice enhances antioxidant capacity and regulates antioxidant gene expression in rat liver, brain and colon

To explore the effect of fruit and vegetable (FV) juice on biomarkers of oxidative damage and antioxidant gene expression in rats, 36 adult male Wistar rats were randomly divided into control, low FV juice dosage or high FV juice dosage treatment groups. The rats were given freshly extracted FV juice or the same volume of saline water daily for five weeks. After intervention, serum and tissues specimens were collected for biomarker and gene expression measurement. FV juice intervention increased total antioxidant capacity, glutathione, vitamin C, β-carotene, total polyphenols, flavonoids levels andglutathione peroxidaseenzyme activity in rat serum or tissues (p < 0.05). FV juice intervention caused reduction of malondialdehyde levels in rat liver (p < 0.05) and significantly modulated transcript levels of glutamate cysteine ligase catalytic subunit (GCLC) and NAD(P)H:quinone oxidoreductase l (NQO1)in rat liver and brain (p < 0.05). The results underline the potential of FV juice to improve the antioxidant capacity and to prevent the oxidative damage in liver, brain and colon.

Chronic maternal calcium and 25-hydroxyvitamin D deficiency in Wistar rats programs abnormal hepatic gene expression leading to hepatic steatosis in female offspring

Importance of calcium and vitamin D deficiency is well established in adult dyslipidemia. We hypothesized that maternal calcium and vitamin D deficiency could alter offspring's lipid metabolism. Our objective was to investigate the effect of maternal dietary calcium and vitamin D deficiency on lipid metabolism and liver function of the F1 generation offspring. intergenerational calcium-deficient (CaD) and vitamin D-deficient (VDD) models were developed by mating normal male rats with deficient females and continuing maternal-deficient diets through pregnancy and lactation. Offspring were fed on control diet post-weaning and studied till 30 weeks. Lipid profile, serum glutamate pyruvate transaminase (SGPT), calcium and vitamin D levels were analyzed. Liver fat deposition, omega-3 fatty acids level and mRNA expression levels of peroxisome proliferator-activated receptor-alpha (PPAR-α), sterol regulatory element-binding protein 1c (SREBP-1c), interleukin 6 (IL-6), superoxide dismutase 1 (SOD-1) and uncoupling protein 2 (UCP2) were determined. Low serum vitamin D levels with an increase in SGPT and TG levels in CaD and VDD female offspring were observed. Severe liver steatosis with down-regulation of PPAR-α and UCP2 and up-regulation of SREBP-1c, IL-6 and SOD-1 was observed in the female offspring born to deficient dams. CaD and VDD male offspring showed mild steatosis and down-regulation of UCP2 and SOD-1. We conclude that maternal calcium and vitamin D deficiency programs abnormal lipid metabolism and hepatic gene expression in the F1 generation female offspring leading to hepatic steatosis, despite feeding them on control diet post-weaning.

PROTECTIVE EFFECT OF MORINGA PEREGRINA LEAVES EXTRACT ON ACETAMINOPHEN -INDUCED LIVER TOXICITY IN ALBINO RATS

BACKGROUND

Acetaminophen is a common antipyretic drug but at overdose can cause severe hepatotoxicity that may further develop into liver failure and hepatic centrilobular necrosis in experimental animals and humans. This study was undertaken to assess the ameliorative role of Moringa peregrina leaves extract against acetaminophen toxicity in rats.

MATERIALS AND METHODS

Induction of hepatotoxicity was done by chronic oral administration of acetaminophen (750 mg/kg bwt) for 4 weeks. To study the possible hepatoprotective effect, Moringa peregrina leaves extract (200 mg/kg bwt) or Silymarin (50 mg/kg bwt) was administered orally, for 4 weeks, along with acetaminophen.

RESULTS

acetaminophen significantly increased serum liver enzymes and caused oxidative stress, evidenced by significantly increased tissue malondialdehyde, glutathione peroxidase, hepatic DNA fragmentation, and significant decrease of glutathione and antioxidant enzymes in liver, blood and brain. On the other hand, administration of Moringa peregrina leaves extract reversed acetaminophen-related toxic effects through: powerful malondialdehyde suppression, glutathione peroxidase normalization and stimulation of the cellular antioxidants synthesis represented by significant increase of glutathione, catalase and superoxide dismutase in liver, blood and brain, besides, DNA fragmentation was significantly decreased in the liver tissue.

CONCLUSION

acetaminophen induced oxidative damage can be improved by Moringa peregrina leaves extract-treatment, due to its antioxidant potential.

Coenzyme Q10 and Oxidative Stress: Inflammation Status in Hepatocellular Carcinoma Patients after Surgery

(1) Background: Hepatocellular carcinoma (HCC) is the second leading cause of cancer deaths worldwide, and surgical resection is the main treatment for HCC. To date, no published study has examined the status of coenzyme Q10 in patients with HCC after surgery. Thus, the purpose of this study was to investigate the correlations between the level of coenzyme Q10, oxidative stress, and inflammation in patients with HCC after surgery; (2) Methods: 71 primary HCC patients were recruited. Levels of coenzyme Q10, vitamin E, oxidative stress (malondialdehyde), antioxidant enzymes activity (superoxidase dismutase, catalase, and glutathione peroxidase), and inflammatory markers (high sensitivity C-reactive protein; tumor necrosis factor-α; and interleukin-6) were measured; (3) Results: Patients with HCC had a significantly lower levels of coenzyme Q10 (p = 0.01) and oxidative stress (p < 0.01), and significantly higher levels of antioxidant enzymes activities and inflammation after surgery (p < 0.05). The level of coenzyme Q10 was significantly positively correlated with antioxidant capacity (vitamin E and glutathione peroxidase activity) and negatively correlated with inflammation markers after surgery; (4) Conclusion: Hepatocarcinogenesis is associated with oxidative stress, and coenzyme Q10 may be considered an antioxidant therapy for patients with HCC, particularly those with higher inflammation after surgery.

Sirtuin 2 aggravates postischemic liver injury by deacetylating mitogen-activated protein kinase phosphatase-1

Sirtuin 2 (Sirt2) is known to negatively regulate anoxia-reoxygenation injury in myoblasts. Because protein levels of Sirt2 are increased in ischemia-reperfusion (I/R)-injured liver tissues, we examined whether Sirt2 is protective or detrimental against hepatic I/R injury. We overexpressed Sirt2 in the liver of C57BL/6 mice using a Sirt2 adenovirus. Wild-type and Sirt2 knockout mice were subjected to a partial (70%) hepatic ischemia for 45 minutes, followed by various periods of reperfusion. In another set of experiments, wild-type mice were pretreated intraperitoneally with AGK2, a Sirt2 inhibitor. Isolated hepatocytes and Kupffer cells from wild-type and Sirt2 knockout mice were subjected to hypoxia-reoxygenation injury to determine the in vitro effects of Sirt2. Mice subjected to I/R injury showed typical patterns of hepatocellular damage. Prior injection with Sirt2 adenovirus aggravated liver injury, as demonstrated by increases in serum aminotransferases, prothrombin time, proinflammatory cytokines, hepatocellular necrosis and apoptosis, and neutrophil infiltration relative to control virus-injected mice. Pretreatment with AGK2 resulted in significant improvements in serum aminotransferase levels and histopathologic findings. Similarly, experiments with Sirt2 knockout mice also revealed reduced hepatocellular injury. The molecular mechanism of Sirt2's involvement in this aggravation of hepatic I/R injury includes the deacetylation and inhibition of mitogen-activated protein kinase phosphatase-1 and consequent activation of mitogen-activated protein kinases.

CONCLUSION

Sirt2 is an aggravating factor during hepatic I/R injury. (Hepatology 2017;65:225-236).

Dicranostiga leptopodu (Maxim.) Fedde extracts attenuated CCl4-induced acute liver damage in mice through increasing anti-oxidative enzyme activity to improve mitochondrial function

Dicranostiga Leptodu (Maxim.) fedde (DLF), a poppy plant, has been reported have many benefits and medicinal properties, including free radicals scavenging and detoxifying. However, the protective effect of DLF extracts against carbon tetrachloride (CCl₄)-induced damage in mice liver has not been elucidated. Here, we demonstrated that DLF extracts attenuated CCl₄-induced liver damage in mice through increasing anti-oxidative enzyme activity to improve mitochondrial function. In this study, the mice liver damage evoked by CCl₄ was marked by morphology changes, significant rise in lipid peroxidation, as well as alterations of mitochondrial respiratory function. Interestingly, pretreatment with DLF extracts attenuated CCl₄-induced morphological damage and increasing of lipid peroxidation in mice liver. Additionally, DLF extracts improved mitochondrial function by preventing the disruption of respiratory chain and suppression of mitochondrial Na⁺K⁺-ATPase and Ca²⁺-ATPase activity. Furthermore, administration with DLF extracts elevated superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) levels and maintained the balance of redox status. This results showed that toxic protection effect of DLF extracts on mice liver is mediated by improving mitochondrial respiratory function and keeping the balance of redox status, which suggesting that DLF extracts could be used as potential toxic protection agent for the liver against hepatotoxic agent.

Reactive oxygen species and antioxidant defense in human gastrointestinal diseases

Crohn's disease and ulcerative colitis, known together as inflammatory bowel diseases (IBDs), and celiac disease are the most common disorders affecting not only adults but also children. Both IBDs and celiac disease are associated with oxidative stress, which may play a significant role in their etiologies. Reactive oxygen species (ROS) such as superoxide radicals (O2•-), hydroxyl radicals (•OH), hydrogen peroxide (H2O2), and singlet oxygen (1O2) are responsible for cell death via oxidation of DNA, proteins, lipids, and almost any other cellular constituent. To protect biological systems from free radical toxicity, several cellular antioxidant defense mechanisms exist to regulate the production of ROS, including enzymatic and nonenzymatic pathways. Superoxide dismutase catalyzes the dismutation of O2•- to H2O2 and oxygen. The glutathione redox cycle involves two enzymes: glutathione peroxidase, which uses glutathione to reduce organic peroxides and H2O2; and glutathione reductase, which reduces the oxidized form of glutathione with concomitant oxidation of nicotinamide adenine dinucleotide phosphate. In addition to this cycle, GSH can react directly with free radicals. Studies into the effects of free radicals and antioxidant status in patients with IBDs and celiac disease are scarce, especially in pediatric patients. It is therefore very necessary to conduct additional research studies to confirm previous data about ROS status and antioxidant activities in patients with IBDs and celiac disease, especially in children.

Induction of Nrf2-mediated phase II detoxifying/antioxidant enzymes in vitro by chitosan-caffeic acid against hydrogen peroxide-induced hepatotoxicity through JNK/ERK pathway

Chemical modification of chitosan is a promising method for the improvement of biological activity. In this study, chitosan-caffeic acid (CCA) was prepared and its in vitro hepatoprotective ability against hydrogen peroxide-induced hepatic damage in liver cells was evaluated. Treatment with CCA (50-400 µg/mL) did not show cytotoxicity and also significantly (p < 0.05) recovered cell viability against 650 µM hydrogen peroxide-induced hepatotoxicity. CCA treatment attenuated reactive oxygen species generation and lipid peroxidation in addition to increasing cellular glutathione level in cultured hepatocytes. To validate the underlying mechanism, antioxidant and phase II detoxifying enzyme expressions, which are mediated by NF-E2-related factor 2 (Nrf2) activation, were analyzed and CCA treatment was found to increase the expression of superoxide dismutase-1 (SOD-1), glutathione reductase (GR), heme oxygenase-1 (HO-1), and NAD(P)H:quinine oxidoreductase 1 (NQO1). CCA treatment resulted in increased Nrf2 nuclear translocation. The phosphorylation of extracellular regulated kinase (ERK), c-Jun NH₂-terminal kinase (JNK), and p38 mitogen-activated protein kinase (MAPK) by CCA treatment contributed to Nrf2 activation. Pharmacological blockade of ERK, JNK, and p38 MAPK revealed that SP600125 (JNK inhibitor) and PD98059 (ERK inhibitor) treatment reduced Nrf2 translocation into the nucleus while SB203580 (p38 inhibitor) exhibited weak inhibition. Collectively, CCA protects liver cells against hydrogen peroxide-induced injury and this ability is attributed to the induction of antioxidants and phase II detoxifying enzymes that are mediated by Nrf2 translocation via JNK/ERK signaling.

Effects of coenzyme Q10 supplementation on antioxidant capacity and inflammation in hepatocellular carcinoma patients after surgery: a randomized, placebo-controlled trial

Background

It has been reported that higher levels of oxidative stress and inflammation play a key role in the progression of hepatocellular carcinoma (HCC) after surgery. Coenzyme Q10 is an endogenous lipid-soluble antioxidant. To date, no intervention study has investigated coenzyme Q10 supplementation in HCC patients after surgery. The purpose of this study was to investigate oxidative stress, antioxidant enzymes activity, and inflammation levels in HCC patients after surgery following administration of coenzyme Q10 (300 mg/day).

Methods

This study was designed as a single-blinded, randomized, parallel, placebo-controlled study. Patients who were diagnosed with primary HCC (n = 41) and were randomly assign to a placebo (n = 20) or coenzyme Q10 (300 mg/day, n = 21) group after surgery. The intervention lasted for 12 weeks. Plasma coenzyme Q10, vitamin E, oxidative stress antioxidant enzymes activity and inflammatory markers levels were measured.

Results

The oxidative stress (p = 0.04) and inflammatory markers (hs-CRP and IL-6, p < 0.01) levels were significantly decreased, and the antioxidant enzymes activity was significantly increased (p < 0.01) after 12 weeks of coenzyme Q10 supplementation. In addition, the coenzyme Q10 level was significantly negatively correlated with the oxidative stress (p = 0.01), and positively correlated with antioxidant enzymes activity (SOD, p = 0.01; CAT, p < 0.05; GPx, p = 0.04) and vitamin E level (p = 0.01) after supplementation.

Conclusion

In conclusion, we demonstrated that a dose of 300 mg/d of coenzyme Q10 supplementation significantly increased the antioxidant capacity and reduced the oxidative stress and inflammation levels in HCC patients after surgery.

Trial registration

Clinical Trials.gov Identifier: NCT01964001

Protective Effect of Bioactivity Guided Fractions of Ziziphus jujuba Mill. Root Bark against Hepatic Injury and Chronic Inflammation via Inhibiting Inflammatory Markers and Oxidative Stress

The tribal communities of North Eastern India rely on herbal medicine to cure various disease conditions. Ziziphus jujuba Mill. (Rhamnaceae) is one of such medicinal plants used for curing liver ailments, insomnia, anemia, diarrhea, diabetic complications, cancer, and loss of appetite. The present study was aimed to describe the protective ability of Z. jujuba root bark (ZJRB) against hepatic injury and chronic inflammation. Bioactivity guided fractionation of Z. jujuba methanol extract (ZJME) was performed using different solvents of increasing polarity viz. hexane (ZJHF), chloroform (ZJCF), ethyl acetate (ZJEAF), water (ZJWF), and residue (ZJMR). In vitro antioxidant results revealed that both ZJME and ZJWF possess strong antioxidant activity among all the fractions and mother extract tested. Further, ZJME and ZJWF showed significant protection against CCl4 intoxicated HepG2 cell lines by means of increased cell viability and decreased LDH levels compared to control group. ZJME at 200, 400 mg/kg and ZJWF at 50, 100 mg/kg inhibited the lipid peroxidation and significantly restored the liver function markers (AST, ALT, ALP, LDH, SOD, and CAT) and cytokine levels (TNF-α, Il-1β, and Il-10) in CCl4 induced acute liver damage in rats. All the results were comparable with standard drug silymarin which was further confirmed by histopathology analysis of liver. Similarly, inflammation and increase inflammatory cytokines levels of carrageenan induced paw edema in rats have been refurbished to normal levels on par with the standard drug indomethacin. ZJWF demonstrated potent response than ZJME in all the biological tests conducted. The results of the study signify the ability of ZJRB as good therapeutic agent for liver toxicity and chronic inflammation.

Noninvasive mapping of the redox status of dimethylnitrosamine-induced hepatic fibrosis using in vivo dynamic nuclear polarization-magnetic resonance imaging

Hepatic fibrosis is a chronic disorder caused by viral infection and/or metabolic, genetic and cholestatic disorders. A noninvasive procedure that enables the detection of liver fibrosis based on redox status would be useful for disease identification and monitoring, and the development of treatments. However, an appropriate technique has not been reported. This study describes a novel method for assessing the redox status of the liver using in vivo dynamic nuclear polarization-magnetic resonance imaging (DNP-MRI) with the nitroxyl radical carbamoyl-PROXYL as a molecular imaging probe, which was tested in dimethylnitrosamine-treated mice as a model of liver fibrosis. Based on the pharmacokinetics of carbamoyl-PROXYL in control livers, reduction rate mapping was performed in fibrotic livers. Reduction rate maps demonstrated a clear difference between the redox status of control and fibrotic livers according to the expression of antioxidants. These findings indicate that in vivo DNP-MRI with a nitroxyl radical probe enables noninvasive detection of changes in liver redox status.

Plasma Malondialdehyde (MDA): An Indication of Liver Damage in Women with Pre-Eclamsia

BACKGROUND

One of the features associated with pre-eclampsia is elevated liver transaminases. The reason this happens has not been fully described. However, the hepatocytes are not known to be spared by free radical injury. This study was conducted to examine the relationship between product of free radical injury (malondialdehyde) and transaminases in pre-eclamptic women.

PATIENTS AND METHODS

A total of 98 and 115 pre-eclamptic and apparently normal pregnant women were selected from the booking clinic of Ladoke Akintola University of Technology Teaching Hospital, Osogbo. Non-pregnant women were selected from volunteered members of staff. Malondialdehyde (MDA), aspartate transaminase (AST) and alanine transaminase (ALT) analyses were determined on collected venous blood sample. Statistical analyses of variables were done using SPSS 17 taking level of significance to be p<0.05.

RESULTS

Subjects with plasma AST between 10 and 20U/L had mean plasma MDA of 0.92µmol/l whereas those with plasma levels greater than 41U/L had mean plasma MDA of 4.72µmol/l. Similarly, Subjects with plasma ALT between 10 and 20U/L had mean plasma MDA of 0.86µmol/l, and subjects with plasma ALT greater than 51 U/L had mean plasma MDA of 4.71µmol/l. Positive correlation was observed between AST and ALT(r=0.79; p=0.047), between AST and MDA(r=0.690; p=0.061) as well as between ALT and MDA(r=0.571; p=0.049).

CONCLUSION

The elevated liver enzymes seen in women with pre-eclampsia may be due to free radical injury to the liver. Pre-eclamptic women without free radical injury did not have elevated transaminases.

Interplay of genetic and epigenetic alterations in hepatocellular carcinoma

Genetic and epigenetic alterations play prominent roles in hepatocarcinogenesis and their appearance varies depending on etiological factors, race and tumor progression. Intriguingly, distinct patterns of these genetic and epigenetic mutations are coupled not only to affect each other, but to trigger different types of tumorigenesis. The patterns and frequencies of somatic variations vary depending on the nature of the surrounding chromatin. On the other hand, epigenetic alterations often induce genomic instability prone to mutation. Therefore, genetic mutations and epigenetic alterations in hepatocellular carcinoma appear to be inseparable factors that accelerate tumorigenesis synergistically. We have summarized recent findings on genetic and epigenetic modifications, their influences on each other's alterations and putative roles in liver tumorigenesis.

Connexin32 deficiency exacerbates carbon tetrachloride-induced hepatocellular injury and liver fibrosis in mice

OBJECTIVE

Liver fibrosis results from the perpetuation of the normal wound healing response to several types of injury. Despite the wealth of knowledge regarding the involvement of intracellular and extracellular signaling pathways in liver fibrogenesis, information about the role of intercellular communication mediated by gap junctions is scarce.

METHODS

In this study, liver fibrosis was chemically induced by carbon tetrachloride in mice lacking connexin32, the major liver gap junction constituent. The manifestation of liver fibrosis was evaluated based on a series of read-outs, including collagen morphometric and mRNA analysis, oxidative stress, apoptotic, proliferative and inflammatory markers.

RESULTS

More pronounced liver damage and enhanced collagen deposition were observed in connexin32 knockout mice compared to wild-type animals in experimentally triggered induced liver fibrosis. No differences between both groups were noticed in apoptotic signaling nor in inflammation markers. However, connexin32 deficient mice displayed decreased catalase activity and increased malondialdehyde levels.

CONCLUSION

These findings could suggest that connexin32-based signaling mediates tissue resistance against liver damage by the modulation of the antioxidant capacity. In turn, this could point to a role for connexin32 signaling as a therapeutic target in the treatment of liver fibrosis.

Caveolin-1 protects against hepatic ischemia/reperfusion injury through ameliorating peroxynitrite-mediated cell death

Nitrative stress is considered as an important pathological process of hepatic ischemia and reperfusion injury but its regulating mechanisms are largely unknown. In this study, we tested the hypothesis that caveolin-1 (Cav-1), a plasma membrane scaffolding protein, could be an important cellular signaling against hepatic I/R injury through inhibiting peroxynitrite (ONOO(-))-induced cellular damage. Male wild-type mice and Cav-1 knockout (Cav-1(-/-)) were subjected to 1h hepatic ischemia following 1, 6 and 12h of reperfusion by clipping and releasing portal vessels respectively. Immortalized human hepatocyte cell line (L02) was subjected to 1h hypoxia and 6h reoxygenation and treated with Cav-1 scaffolding domain peptide. The major discoveries included: (1) the expression of Cav-1 in serum and liver tissues of wild-type mice was time-dependently elevated during hepatic ischemia-reperfusion injury. (2) Cav-1 scaffolding domain peptide treatment inhibited cleaved caspase-3 expression in the hypoxia-reoxygenated L02 cells; (3) Cav-1 knockout (Cav-1(-/-)) mice had significantly higher levels of serum transaminases (ALT&AST) and TNF-α, and higher rates of apoptotic cell death in liver tissues than wild-type mice after subjected to 1h hepatic ischemia and 6hour reperfusion; (4) Cav-1(-/-) mice revealed higher expression levels of iNOS, ONOO(-) and 3-nitrotyrosine (3-NT) in the liver than wild-type mice, and Fe-TMPyP, a representative peroxynitrite decomposition catalyst (PDC), remarkably reduced level of ONOO(-) and 3-NT and ameliorated the serum ALT, AST and TNF-α levels in both wild-type and Cav-1(-/-) mice. Taken together, we conclude that Cav-1 could play a critical role in preventing nitrative stress-induced liver damage during hepatic ischemia-reperfusion injury.

Amomum cardamomum L. ethyl acetate fraction protects against carbon tetrachloride-induced liver injury via an antioxidant mechanism in rats

Background

Medicinal herb-derived drug development has become important in the relief of liver pathology. Amomun cardamomum is traditionally used therapeutically in Korea to treat various human ailments including dyspepsia, hiccupping, and vomiting. We investigated to assess the protective effect of A. cardamomum on carbon tetrachloride (CCl₄)-induced liver damage through antioxidant activity in hepatic tissues of Sprague–Dawley rats.

Methods

Antioxidant properties of different fractions from A. cardamomum from ethanol extracts were evaluated by an in vitro free radical scavenging systems. The protective effect of the ethyl acetate fraction from A. cardamomum (EAAC) against CCl₄-induced cytotoxicity was determined by a cell viability assay using HepG2 hepatocarcinoma cells. In vivo study, the influence of EAAC concentrations of 100 and 200 mg/kg following CCl₄-induced hepatic injury was assessed. Serum levels of glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), and alkaline phosphatase (ALP) were determined, as was lipid peroxidation (malondialdehyde, MDA). Effect of EAAC on liver detoxification enzymes including superoxide dismutase (SOD), total glutathione (GSH), and glutathione S-transferase (GST) activity was measured in rat liver homogenates. Liver cytochrome P450 (CYP2E1) expression level was determined by quantification of mRNA.

Results

Phytochemical analysis of A. cardamomum indicated that EAAC was enriched in total polyphenol and total flavonoid. Most of the tannins were confined to the hexane fraction. Hepatoprotective properties of EAAC were evident, with significantly reduced serum levels of GOT, GPT, and ALP compared with the control group. Improved hepatic antioxidant status was evident by increased SOD, GSH, and GST enzymes in rat liver tissue. Liver lipid peroxidation induced by CCl₄ was apparent by increased intracellular MDA level. EAAC suppressed lipid peroxidation as evidenced by the significant decrease in MDA production. Expression of CYP2E1 was also significantly decreased at the higher concentration of EAAC, indicating the hepatoprotective efficacy of EAAC on acute liver damage.

Conclusion

These results indicated that EAAC has a significant hepatoprotective activity on CCl₄-induced acute hepatic injury in rats, which might be derived from its antioxidant properties and CYP2E1 downregulation.

Protective Effects of Royal Jelly on Oxymetholone-Induced Liver Injury in Mice

Background:

The present study was carried out to investigate the possible protective effects of royal jelly (RJ) on oxymetholone (OXM)-induced oxidative liver injuries in mice.

Methods:

In total, 32 adult male NMRI mice were divided into four groups of eight mice each. Mice in groups 1 and 2 were orally administered 5 mg/kg/day OXM for 30 days. At the same time, mice in group 3 received RJ at a dose of 100 mg/kg/day. Saline control and RJ control groups were also included in this study.

Results:

Administration of 5 mg/kg OXM resulted in a significant decrease in total antioxidant capacity and catalase activity, as well as a significant increase in malondialdehyde (P<0.05). In addition, OXM-administrated mice showed a slight increase in liver enzymes, including alanine amino transferase, aspartate amino transferase, and alkaline phosphatase. Although OXM caused histopathological changes in the liver, RJ could significantly improve all of the above-mentioned parameters at a dose of 100 mg/kg.

Conclusion:

The results of the present study indicated that RJ has a partially protective effect on OXM-induced liver toxicity in mice.

l-carnitine protects human hepatocytes from oxidative stress-induced toxicity through Akt-mediated activation of Nrf2 signaling pathway

In our previous study, l-carnitine was shown to have cytoprotective effect against hydrogen peroxide (H2O2)-induced injury in human normal HL7702 hepatocytes. The aim of this study was to investigate whether the protective effect of l-carnitine was associated with the nuclear factor erythroid 2 (NFE2)-related factor 2 (Nrf2) pathway. Our results showed that pretreatment with l-carnitine augmented Nrf2 nuclear translocation, DNA binding activity and heme oxygenase-1 (HO-1) expression in H2O2-treated HL7702 cells, although l-carnitine treatment alone had no effect on them. Analysis using Nrf2 siRNA demonstrated that Nrf2 activation was involved in l-carnitine-induced HO-1 expression. In addition, l-carnitine-mediated protection against H2O2 toxicity was abrogated by Nrf2 siRNA, indicating the important role of Nrf2 in l-carnitine-induced cytoprotection. Further experiments revealed that l-carnitine pretreatment enhanced the phosphorylation of Akt in H2O2-treated cells. Blocking Akt pathway with inhibitor partly abrogated the protective effect of l-carnitine. Moreover, our finding demonstrated that the induction of Nrf2 translocation and HO-1 expression by l-carnitine directly correlated with the Akt pathway because Akt inhibitor showed inhibitory effects on the Nrf2 translocation and HO-1 expression. Altogether, these results demonstrate that l-carnitine protects HL7702 cells against H2O2-induced cell damage through Akt-mediated activation of Nrf2 signaling pathway.

Oxidative stress balance is dysregulated and represents an additional target for treating cholangiocarcinoma

BACKGROUND

Pancreatico-biliary malignancies exhibit similar characteristics, including obesity-related features and poor prognosis, and require new treatment strategies. Oxidative stress is known to induce DNA damage and carcinogenesis, and its reduction is viewed as being favorable. However, it also has anti-infection and anti-cancer functions that need to be maintained. To reveal the effect of oxidative stress on cancer progression, we evaluated oxidative stress and anti-oxidative balance in pancreatic cancer (PC) and cholangiocarcinoma (CC) patients, as well as the effect of add-on antioxidant treatment to chemotherapy in a mouse cholangiocarcinoma model.

METHODS

We recruited 84 CC and 80 PC patients who were admitted to our hospital. Serum levels of reactive oxygen metabolites (ROM) and the anti-oxidative OXY-adsorbent test were determined and the balance of these tests was defined as an oxidative index. A diabetic mouse-based cholangiocarcinoma model was utilized to evaluate the effects of add-on antioxidant therapy on cholangiocarcinoma chemotherapy.

RESULTS

Serum ROM was higher and anti-oxidant OXY was lower in CC patients with poor outcomes. These parameters were not significantly different in PC patients. In mice, vitamin E administration induced antioxidant hemeoxygenase (HO)-1 protein expression in cancer tissue, while the number of stem-like cells increased. l-carnitine administration improved intestinal microbiome and biliary acid balance, upregulated the hepatic mitochondrial membrane uptake related gene Cpt1 in non-cancerous tissue, and did not alter stem-like cell numbers.

CONCLUSION

Oxidative stress balance was dysregulated in cholangiocarcinoma with poor outcome. The mitochondrial function-supporting agent l-carnitine is a good candidate to control oxidative stress conditions.

Crosstalk between liver antioxidant and the endocannabinoid systems after chronic administration of the FAAH inhibitor, URB597, to hypertensive rats

Hypertension is accompanied by perturbations to the endocannabinoid and antioxidant systems. Thus, potential pharmacological treatments for hypertension should be examined as modulators of these two metabolic systems. The aim of this study was to evaluate the effects of chronic administration of the fatty acid amide hydrolase (FAAH) inhibitor [3-(3-carbamoylphenyl)phenyl]N-cyclohexylcarbamate (URB597) on the endocannabinoid system and on the redox balance in the livers of DOCA-salt hypertensive rats. Hypertension caused an increase in the levels of endocannabinoids [anandamide (AEA), 2-arachidonoyl-glycerol (2-AG) and N-arachidonoyl-dopamine (NADA)] and CB1 receptor and the activities of FAAH and monoacylglycerol lipase (MAGL). These effects were accompanied by an increase in the level of reactive oxygen species (ROS), a decrease in antioxidant activity/level, enhanced expression of transcription factor Nrf2 and changes to Nrf2 activators and inhibitors. Moreover, significant increases in lipid, DNA and protein oxidative modifications, which led to enhanced levels of proapoptotic caspases, were also observed. URB597 administration to the hypertensive rats resulted in additional increases in the levels of AEA, NADA and the CB1 receptor, as well as decreases in vitamin E and C levels, glutathione peroxidase and glutathione reductase activities and Nrf2 expression. Thus, after URB597 administration, oxidative modifications of cellular components were increased, while the inflammatory response was reduced. This study revealed that chronic treatment of hypertensive rats with URB597 disrupts the endocannabinoid system, which causes an imbalance in redox status. This imbalance increases the levels of electrophilic lipid peroxidation products, which later participate in metabolic disturbances in liver homeostasis.

Biomarkers of Flutamide-Bioactivation and Oxidative Stress In Vitro and In Vivo

The nonsteroidal androgen-receptor antagonist flutamide is associated with hepatic injury. Oxidative stress and reactive metabolite formation are considered contributing factors to liver toxicity. Here we have used flutamide as a model drug to study the generation of reactive drug metabolites that undergo redox cycling to induce oxidative stress (OS) in vitro and in vivo. Lipid peroxidation (LPO) markers, as well as genes regulated by the redox-sensitive Nrf2 pathway, have been identified as surrogates for the characterization of OS. These markers and metabolism biomarkers for drug bioactivation have been investigated to characterize drug-induced hepatic damage. Rat hepatocytes and in vivo studies showed that several LPO markers, namely the isoprostanes 15R-PD2, dihydro keto PE2, and iPF(2α)-VI, as well as hydroxynonenal mercapturic acid metabolites, had increased significantly by 24 hours after flutamide treatment from 4.9 to 15.3-fold in hepatocytes and from 2.6 to 31.0-fold in rat plasma. Induction of mRNA expression levels for Nrf2-regulated genes was evident as well, with heme oxygenase 1, glutathione-S-transferase π1 and NAD(P)H dehydrogenase showing a 3.6-, 4.1-, and 1.9-fold increase in hepatocytes and 5.6-, 7.5-, and 94.1-fold in rat liver. All effects were observed at drug concentrations that did not show overt liver toxicity. Addition of an in situ hydrogen peroxide-generating system to in vitro experiments demonstrated the formation of a reactive di-imine intermediate as the responsible metabolic pathway for the generation of OS. The dataset suggests that hepatic oxidative stress conditions can be mediated via metabolic activation and can be monitored with suitable biomarkers preceding the terminal damage.

Different Contribution of Redox-Sensitive Transient Receptor Potential Channels to Acetaminophen-Induced Death of Human Hepatoma Cell Line

Acetaminophen (APAP) is a safe analgesic antipyretic drug at prescribed doses. Its overdose, however, can cause life-threatening liver damage. Though, involvement of oxidative stress is widely acknowledged in APAP-induced hepatocellular death, the mechanism of this increased oxidative stress and the associated alterations in Ca²⁺ homeostasis are still unclear. Among members of transient receptor potential (TRP) channels activated in response to oxidative stress, we here identify that redox-sensitive TRPV1, TRPC1, TRPM2, and TRPM7 channels underlie Ca²⁺ entry and downstream cellular damages induced by APAP in human hepatoma (HepG2) cells. Our data indicate that APAP treatment of HepG2 cells resulted in increased reactive oxygen species (ROS) production, glutathione (GSH) depletion, and Ca²⁺ entry leading to increased apoptotic cell death. These responses were significantly suppressed by pretreatment with the ROS scavengers N-acetyl-L-cysteine (NAC) and 4,5-dihydroxy-1,3-benzene disulfonic acid disodium salt monohydrate (Tiron), and also by preincubation of cells with the glutathione inducer Dimethylfumarate (DMF). TRP subtype-targeted pharmacological blockers and siRNAs strategy revealed that suppression of either TRPV1, TRPC1, TRPM2, or TRPM7 reduced APAP-induced ROS formation, Ca²⁺ influx, and cell death; the effects of suppression of TRPV1 or TRPC1, known to be activated by oxidative cysteine modifications, were stronger than those of TRPM2 or TRPM7. Interestingly, TRPV1 and TRPC1 were labeled by the cysteine-selective modification reagent, 5,5′-dithiobis (2-nitrobenzoic acid)-2biotin (DTNB-2Bio), and this was attenuated by pretreatment with APAP, suggesting that APAP and/or its oxidized metabolites act directly on the modification target cysteine residues of TRPV1 and TRPC1 proteins. In human liver tissue, TRPV1, TRPC1, TRPM2, and TRPM7 channels transcripts were localized mainly to hepatocytes and Kupffer cells. Our findings strongly suggest that APAP-induced Ca²⁺ entry and subsequent hepatocellular death are regulated by multiple redox-activated cation channels, among which TRPV1 and TRPC1 play a prominent role.

The Anti-Oxidant and Antitumor Properties of Plant Polysaccharides

Oxidative stress has been increasingly recognized as a major contributing factor in a variety of human diseases, from inflammation to cancer. Although certain parts of signaling pathways are still under investigation, detailed molecular mechanisms for the induction of diseases have been elucidated, especially the link between excessive oxygen reactive species (ROS) damage and tumorigenesis. Emerging evidence suggests anti-oxidant therapy can play a key role in treating those diseases. Among potential drug resources, plant polysaccharides are natural anti-oxidant constituents important for human health because of their long history in ethnopharmacology, wide availability and few side effects upon consumption. Plant polysaccharides have been shown to possess anti-oxidant, anti-inflammation, cell viability promotion, immune-regulation and antitumor functions in a number of disease models, both in laboratory studies and in the clinic. In this paper, we reviewed the research progress of signaling pathways involved in the initiation and progression of oxidative stress- and cancer-related diseases in humans. The natural sources, structural properties and biological actions of several common plant polysaccharides, including Lycium barbarum, Ginseng, Zizyphus Jujuba, Astragalus lentiginosus, and Ginkgo biloba are discussed in detail, with emphasis on their signaling pathways. All of the mentioned common plant polysaccharides have great potential to treat oxidative stress and cancinogenic disorders in cell models, animal disease models and clinical cases. ROS-centered pathways (e.g. mitochondrial autophagy, MAPK and JNK) and transcription factor-related pathways (e.g. NF-[Formula: see text]B and HIF) are frequently utilized by these polysaccharides with or without the further involvement of inflammatory and death receptor pathways. Some of the polysaccharides may also influence tumorigenic pathways, such as Wnt and p53 to play their anti-tumor roles. In addition, current problems and future directions for the application of those plant polysaccharides are also listed and discussed.

Oxidative Stress and Inflammation in Hepatic Diseases: Therapeutic Possibilities of N-Acetylcysteine

Liver disease is highly prevalent in the world. Oxidative stress (OS) and inflammation are the most important pathogenetic events in liver diseases, regardless the different etiology and natural course. N-acetyl-l-cysteine (the active form) (NAC) is being studied in diseases characterized by increased OS or decreased glutathione (GSH) level. NAC acts mainly on the supply of cysteine for GSH synthesis. The objective of this review is to examine experimental and clinical studies that evaluate the antioxidant and anti-inflammatory roles of NAC in attenuating markers of inflammation and OS in hepatic damage. The results related to the supplementation of NAC in any form of administration and type of study are satisfactory in 85.5% (n = 59) of the cases evaluated (n = 69, 100%). Within this percentage, the dosage of NAC utilized in studies in vivo varied from 0.204 up to 2 g/kg/day. A standard experimental design of protection and treatment as well as the choice of the route of administration, with a broader evaluation of OS and inflammation markers in the serum or other biological matrixes, in animal models, are necessary. Clinical studies are urgently required, to have a clear view, so that, the professionals can be sure about the effectiveness and safety of NAC prescription.

AMPK activation by liquiritigenin inhibited oxidative hepatic injury and mitochondrial dysfunction induced by nutrition deprivation as mediated with induction of farnesoid X receptor

PURPOSE

Nutrition is indispensable for cell survival and proliferation. Thus, loss of nutrition caused by serum starvation in cells could induce formation of reactive oxygen species (ROS), resulting in cell death. Liquiritigenin (LQ) is an active flavonoid in licorice and plays a role in the liver as a hepatic protectant.

METHODS

This study investigated the effect of LQ, metformin [an activator of activated AMP-activated protein kinase (AMPK)] and GW4064 [a ligand of farnesoid X receptor (FXR)] on mitochondrial dysfunction and oxidative stress induced by serum deprivation as well as its molecular mechanism, as assessed by immunoblot and flow cytometer assays.

RESULTS

Serum deprivation in HepG2, H4IIE and AML12 cells successfully induced oxidative stress and apoptosis, as indicated by depletion of glutathione, formation of ROS, and altered expression of apoptosis-related proteins such as procaspase-3, poly(ADP-ribose) polymerase, and Bcl-2. However, LQ pretreatment significantly blocked these pathological changes and mitochondrial dysfunction caused by serum deprivation. Moreover, LQ activated AMPK in HepG2 cells and mice liver, as shown by phosphorylation of AMPK and ACC, and this activation was mediated by its upstream kinase (i.e., LKB1). Experiments using a chemical inhibitor of AMPK with LKB1-deficient Hela cells revealed the role of the LKB1-AMPK pathway in cellular protection conferred by LQ. LQ also induced protein and mRNA expression of both FXR as well as small heterodimer partner, which is important since treatment with FXR ligand GW4064 protected hepatocytes against cell death and mitochondrial damage induced by serum deprivation.

CONCLUSION

AMPK activators such as LQ can protect hepatocytes against oxidative hepatic injury and mitochondrial dysfunction induced by serum deprivation, and the beneficial effect might be mediated through the LKB1 pathway as well as FXR induction.

Rhus javanica Linn protects against hydrogen peroxide‑induced toxicity in human Chang liver cells via attenuation of oxidative stress and apoptosis signaling

Rhus javanica Linn, a traditional medicinal herb from the family Anacardiaceae, has been used in the treatment of liver diseases, cancer, parasitic infections, malaria and respiratory diseases in China, Korea and other Asian countries for centuries. In the present study, the protective effects of R. javanica ethanolic extract (RJE) on hydrogen peroxide (H2O2)-induced oxidative stress in human Chang liver cells was investigated. The cell cytotoxicity and viability were assessed using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The activities of superoxide dismutase (SOD) and catalase (CAT) were measured using respective enzymatic kits. Cell cycle analysis was performed using flow cytometric analysis. The protein expression levels of p53, B-cell lymphoma (Bcl)-2, Bcl-2-associated X protein (Bax) and caspase-3 were assessed by western blotting. Human Chang liver cells were treated with different concentrations (0.1, 0.3 or 0.5 mg/ml) of RJE, and were subsequently exposed to H2O2 (30 µM). Treatment with H2O2 (30 µM) significantly induced cytotoxicity (P<0.05) and reduced the viability of the Chang liver cells. However, pretreatment of the cells with RJE (0.1, 0.3 or 0.5 mg/ml) significantly increased the cell viability (P<0.001 at 0.5 mg/ml) in a concentration-dependent manner following H2O2 treatment. Furthermore, pretreatment with RJE increased the enzyme activities of SOD and CAT, and decreased the sub-G1 growth phase of the cell cycle in response to H2O2-induced oxidative stress (P<0.001 at 0.3 and 0.5 mg/ml H2O2). RJE also regulated the protein expression levels of p53, Bax, caspase-3 and Bcl-2. These results suggested that RJE may protect human Chang liver cells against oxidative damage by increasing the levels of antioxidant enzymes and regulating antiapoptotic oxidative stress mechanisms, thereby providing insights into the mechanism which underpins the traditional claims made for RJE in the treatment of liver diseases.

Critical review of resveratrol in xenobiotic-induced hepatotoxicity

Use of natural products is increasingly popular. In fact, many patients with liver diseases self-medicate with herbal supplements. Resveratrol (RSV), in particular, is a common natural product that can reduce injury in experimental models of liver disease. Xenobiotic hepatotoxicity is a particularly important area-of-need for therapeutics. Drug-induced liver injury, for example, is the most common cause of acute liver failure (ALF) and ALF-induced deaths in many countries. Importantly, RSV protects against hepatotoxicity in animal models in vivo caused by several drugs and chemicals and may be an effective intervention. Although many mechanisms have been proposed to explain the protection, not all are consistent with other data. Furthermore, RSV suffers from other issues, including limited bioavailability due to extensive hepatic metabolism. The purpose of this article is to summarize recent findings on the protective effects of RSV in xenobiotic-induced liver injury and other forms of liver injury and to provide a critical review of the underlying mechanisms. New mechanisms that are more consistent with data emerging from the toxicology field are suggested. Efforts to move RSV into clinical use are also considered. Overall, RSV is a promising candidate for therapeutic use, but additional studies are needed to better understand its effects.

Antioxidant, Hepatoprotective Potential and Chemical Profiling of Propolis Ethanolic Extract from Kashmir Himalaya Region Using UHPLC-DAD-QToF-MS

The aim of this study was to examine hepatoprotective effect of ethanolic extract of propolis (KPEt) from Kashmir Himalaya against isoniazid and rifampicin (INH-RIF) induced liver damage in rats. Hepatic cellular injury was initiated by administration of INH-RIF combination (100 mg/kg) intraperitoneal (i.p.) injection for 14 days. We report the protective effects of KPEt against INH-RIF induced liver oxidative stress, inflammation, and enzymatic and nonenzymatic antioxidants. Oral administration of KPEt at both doses (200 and 400 mg/kg body weight) distinctly restricted all modulating oxidative liver injury markers and resulted in the attenuation of INH-RIF arbitrated damage. The free radical scavenging activity of KPEt was evaluated by DPPH, nitric oxide, and superoxide radical scavenging assay. The components present in KPEt identified by ultra high performance liquid chromatography diode array detector time of flight-mass spectroscopy (UHPLC-DAD-QToF-MS) were found to be flavonoids and phenolic acids. The protective efficacy of KPEt is possibly because of free radical scavenging and antioxidant property resulting from the presence of flavonoids and phenolic acids.

INFLUENCE OF OXIDATIVE STRESS AND OBESITY IN PATIENTS WITH NONALCOHOLIC STEATOHEPATITIS

BackgroundNonalcoholic steatohepatitis is considered the hepatic manifestation of metabolic syndrome and it is particularly associated to the insulin resistance, hypertension, obesity and abnormalities in lipid and glucose metabolism.ObjectiveConsidering the importance of obesity and oxidative stress in the pathophysiology of nonalcoholic steatohepatitis, this study aimed to evaluate the presence and association of the obesity and oxidative stress in this pathology.MethodsFifteen outpatients with nonalcoholic steatohepatitis (nonalcoholic steatohepatitis group), diagnosed according to the histopathological findings from the liver biopsy, and 15 body mass index-matched subjects (non nonalcoholic steatohepatitis group) without nonalcoholic steatohepatitis were included. All volunteers were registered in a Brazilian University Hospital. Nutritional assessment (weight, height, body mass index and waist circumference) and biochemical analysis (fasting glucose, liver enzymes, lipid profile, leptin, superoxide dismutase, glutathione peroxidase, vitamins C and E, catalase and 8-isoprostane) were performed for all the participants. The student t test was used for statistical analysis, with P<0.05 as the significant factor.ResultsNonalcoholic steatohepatitis patients had higher fasting glucose, hepatic enzymes (serum aspartate aminotransaminase, alanine aminotransaminase, gamma glutamyl transferase, alkaline phosphatase), triglycerides and superoxide dismutase and lower glutathione peroxidase values than non nonalcoholic steatohepatitis individuals.ConclusionThis paper demonstrates that only the presence of obesity is not enough to trigger alterations in all the studied biomarkers. Despite the majority of oxidative stress markers being found to be similar in both conditions, the nonalcoholic steatohepatitis subjects could be slightly more affected than the non nonalcoholic steatohepatitis individuals.

Redox regulation of FoxO transcription factors

Transcription factors of the forkhead box, class O (FoxO) family are important regulators of the cellular stress response and promote the cellular antioxidant defense. On one hand, FoxOs stimulate the transcription of genes coding for antioxidant proteins located in different subcellular compartments, such as in mitochondria (i.e. superoxide dismutase-2, peroxiredoxins 3 and 5) and peroxisomes (catalase), as well as for antioxidant proteins found extracellularly in plasma (e.g., selenoprotein P and ceruloplasmin). On the other hand, reactive oxygen species (ROS) as well as other stressful stimuli that elicit the formation of ROS, may modulate FoxO activity at multiple levels, including posttranslational modifications of FoxOs (such as phosphorylation and acetylation), interaction with coregulators, alterations in FoxO subcellular localization, protein synthesis and stability. Moreover, transcriptional and posttranscriptional control of the expression of genes coding for FoxOs is sensitive to ROS. Here, we review these aspects of FoxO biology focusing on redox regulation of FoxO signaling, and with emphasis on the interplay between ROS and FoxOs under various physiological and pathophysiological conditions. Of particular interest are the dual role played by FoxOs in cancer development and their key role in whole body nutrient homeostasis, modulating metabolic adaptations and/or disturbances in response to low vs. high nutrient intake. Examples discussed here include calorie restriction and starvation as well as adipogenesis, obesity and type 2 diabetes.

Phytoextract of Indian mustard seeds acts by suppressing the generation of ROS against acetaminophen-induced hepatotoxicity in HepG2 cells

CONTEXT

Indian mustard [Brassica juncea (L.) Czern. & Coss. (Brassicaceae)] is reported to possess diverse pharmacological properties. However, limited information is available concerning its hepatoprotective activity and mechanism of action.

OBJECTIVE

To study the protective mechanism of mustard seed extract against acetaminophen (APAP) toxicity in a hepatocellular carcinoma (HepG2) cell line.

MATERIALS AND METHODS

Hepatotoxicity models were established using APAP (2.5-22.5 mM) based on the cytotoxicity profile. An antioxidant-rich fraction from mustard seeds was extracted and evaluated for its hepatoprotective potential. The mechanism of action was elucidated using various in vitro antioxidant assays, the detection of intracellular generation of reactive oxygen species (ROS), and cell cycle analysis. The phytoconstituents isolated via HPLC-DAD were also evaluated for hepatoprotective activity.

RESULTS

Hydromethanolic seed extract exhibited hepatoprotective activity in post- and pre-treatment models of 20 mM APAP toxicity and restored the elevated levels of liver indices to normal values (p < 0.05). Post-treatment suppressed the generation of ROS by 58.37% and pre-treatment effectively prevented the generation of ROS by 90.5%. The mechanism of ROS suppression was further supported by antioxidant activity (IC50) data from DPPH (103.37 ± 4.2 µg AAE/mg), FRAP (83.26 ± 1.1 µg AAE/mg), ORAC (1115 µM GAE/ml), ABTS (83.05 µg GAE/ml), and superoxide (345.22 ± 5.15 µg AAE/mg) scavenging assays and by the restoration of cell cycle alterations. HPLC-DAD analysis revealed the presence quercetin, vitamin E, and catechin, which exhibited hepatoprotective activity.

DISCUSSION AND CONCLUSIONS

A phytoextract of mustard seeds acts by suppressing the generation of ROS in response to APAP toxicity.

Nicotinic acid prevents experimental liver fibrosis by attenuating the prooxidant process

Liver fibrosis is the excessive accumulation of extracellular matrix proteins that occurs in most chronic liver diseases. Nicotinamide treatment has been shown to prevent collagen accumulation and fibrogenesis in a bleomycin model of lung fibrosis. In this study, we evaluated the effects of nicotinic acid (NA) on experimental liver fibrosis and investigated its underlying mechanism.

METHODS

Fibrosis was induced by chronic TAA administration and the effects of co-administration with NA for 8 weeks were evaluated, including control groups.

RESULTS

TAA administration induced liver fibrosis, which was prevented by nicotinic acid. NA prevented the elevation of liver enzymes and prevented hepatic glycogen depletion. Liver histopathology and hydroxyproline levels were significantly lower in the rats treated with TAA plus NA compared with TAA only. NA demonstrated antioxidant properties by restoring the redox equilibrium (lipid peroxidation and GPx levels). Western blot assays showed decreased expression levels of TGF-β and its downstream inductor CTGF. Additionally, NA prevented hepatic stellate cell activation due by blocking the expression of α-SMA. Zymography assays showed that NA decreased the activity of matrix metalloproteinases 2 and 9.

CONCLUSIONS

NA prevents experimental fibrosis; the mechanisms of action are associated with its antioxidant properties and the reduction in TGF-β expression. The decrease in TGF-β levels may be associated with the attenuation of the oxidative processes, thus resulting in a reduction in HSC activation and ECM deposition. The findings suggest a possible role for NA as an antifibrotic agent for liver injury.

Increase of glycosaminoglycans and metalloproteinases 2 and 9 in liver extracellular matrix on early stages of extrahepatic cholestasis

CONTEXT

Cholestasis produces hepatocellular injury, leukocyte infiltration, ductular cells proliferation and fibrosis of liver parenchyma by extracellular matrix replacement.

OBJECTIVE

Analyze bile duct ligation effect upon glycosaminoglycans content and matrix metalloproteinase (MMPs) activities.

METHODS

Animals (6-8 weeks; n = 40) were euthanized 2, 7 or 14 days after bile duct ligation or Sham-surgery. Disease evolution was analyzed by body and liver weight, seric direct bilirubin, globulins, gamma glutamyl transpeptidase (GGT), alkaline phosphatase (Alk-P), alanine and aspartate aminotransferases (ALT and AST), tissue myeloperoxidase and MMP-9, pro MMP-2 and MMP-2 activities, histopathology and glycosaminoglycans content.

RESULTS

Cholestasis caused cellular damage with elevation of globulins, GGT, Alk-P, ALT, AST. There was neutrophil infiltration observed by the increasing of myeloperoxidase activity on 7 (P = 0.0064) and 14 (P = 0.0002) groups which leads to the magnification of tissue injuries. Bile duct ligation increased pro-MMP-2 (P = 0.0667), MMP-2 (P = 0.0003) and MMP-9 (P<0.0001) activities on 14 days indicating matrix remodeling and establishment of inflammatory process. Bile duct ligation animals showed an increasing on dermatan sulfate and/or heparan sulfate content reflecting extracellular matrix production and growing mitosis due to parenchyma depletion.

CONCLUSIONS

Cholestasis led to many changes on rats' liver parenchyma, as so as on its extracellular matrix, with major alterations on MMPs activities and glycosaminoglycans content.

Control of oxidative stress in hepatocellular carcinoma: Helpful or harmful?

Oxidative stress is becoming recognized as a key factor in the progression of chronic liver disease (CLD) and hepatocarcinogenesis. The metabolically important liver is a major reservoir of mitochondria that serve as sources of reactive oxygen species, which are apparently responsible for the initiation of necroinflammation. As a result, CLD could be a major inducer of oxidative stress. Chronic hepatitis C is a powerful generator of oxidative stress, causing a high rate of hepatocarcinogenesis among patients with cirrhosis. Non-alcoholic steatohepatitis is also associated with oxidative stress although its hepatocarcinogenic potential is lower than that of chronic hepatitis C. Analyses of serum markers and histological findings have shown that hepatocellular carcinoma correlates with oxidative stress and experimental data indicate that oxidative stress increases the likelihood of developing hepatocarcinogenesis. However, the results of antioxidant therapy have not been favorable. Physiological oxidative stress is a necessary biological response, and thus adequate control of oxidative stress and a balance between oxidative and anti-oxidative responses is important. Several agents including metformin and L-carnitine can reportedly control mechanistic oxidative stress. This study reviews the importance of oxidative stress in hepatocarcinogenesis and of control strategies for the optimal survival of patients with CLD and hepatocellular carcinoma.

l-Theanine prevents carbon tetrachloride-induced liver fibrosis via inhibition of nuclear factor κB and down-regulation of transforming growth factor β and connective tissue growth factor

Here we evaluated the ability of L-theanine in preventing experimental hepatic cirrhosis and investigated the roles of nuclear factor-κB (NF-κB) activation as well as transforming growth factor β (TGF-β) and connective tissue growth factor (CTGF) regulation. Experimental hepatic cirrhosis was established by the administration of carbon tetrachloride (CCl4) to rats (0.4 g/kg, intraperitoneally, three times per week, for 8 weeks), and at the same time, adding L-theanine (8.0 mg/kg) to the drinking water. Rats had ad libitum access to water and food throughout the treatment period. CCl4 treatment promoted NF-κB activation and increased the expression of both TGF-β and CTGF. CCl4 increased the serum activities of alanine aminotransferase and γ-glutamyl transpeptidase and the degree of lipid peroxidation, and it also induced a decrease in the glutathione and glutathione disulfide ratio. L-Theanine prevented increased expression of NF-κB and down-regulated the pro-inflammatory (interleukin (IL)-1β and IL-6) and profibrotic (TGF-β and CTGF) cytokines. Furthermore, the levels of messenger RNA encoding these proteins decreased in agreement with the expression levels. L-Theanine promoted the expression of the anti-inflammatory cytokine IL-10 and the fibrolytic enzyme metalloproteinase-13. Liver hydroxyproline contents and histopathological analysis demonstrated the anti-fibrotic effect of l-theanine. In conclusion, L-theanine prevents CCl4-induced experimental hepatic cirrhosis in rats by blocking the main pro-inflammatory and pro-fibrogenic signals.

Pyrroloquinoline-quinone suppresses liver fibrogenesis in mice

Liver fibrosis represents the consequences of a sustained wound healing response to chronic liver injuries, and its progression toward cirrhosis is the major cause of liver-related morbidity and mortality worldwide. However, anti-fibrotic treatment remains an unconquered area for drug development. Accumulating evidence indicate that oxidative stress plays a critical role in liver fibrogenesis. In this study, we found that PQQ, a natural anti-oxidant present in a wide variety of human foods, exerted potent anti-fibrotic and ROS-scavenging activity in Balb/C mouse models of liver fibrosis. The antioxidant activity of PQQ was involved in the modulation of multiple steps during liver fibrogenesis, including chronic liver injury, hepatic inflammation, as well as activation of hepatic stellate cells and production of extracellular matrix. PQQ also suppressed the up-regulation of RACK1 in activated HSCs in vivo and in vitro. Our data suggest that PQQ suppresses oxidative stress and liver fibrogenesis in mice, and provide rationale for the clinical application of PQQ in the prevention and treatment of liver fibrosis.