Nrf2 and antioxidant defense against CYP2E1 toxicity

Discovery of CYP2E1 as a novel target in rheumatoid arthritis and validation by a new specific CYP2E1 inhibitor

Considerable evidence indicates that CYP2E1 is associated with a variety of inflammatory diseases. Here we evaluated CYP2E1 as a potential therapeutic target for rheumatoid arthritis (RA) and established the protective effect of a new CYP2E1 inhibitor. Gene-expression datasets were used to analyze the change in expression of CYP2E1 in RA patients; CYP2E1 activity in collagen-induced arthritis (CIA) rats was determined by HPLC. We further evaluated the protective effects of Cyp2e1 knockout and a CYP2E1-specific inhibitor, Q11, synthesized by our group, in CIA and adjuvant-induced arthritis (AIA) rats. The expression of CYP2E1 in synovial tissue was elevated in RA patients and in CIA rats and the activity of CYP2E1 in vivo and in vitro in CIA rats was greater than that of controls. Cyp2e1 knockout significantly reduced the incidence of CIA and alleviated the severity of symptoms. Treatment with different doses of Q11 decreased paw thickness, volume and arthritis scores and reduced the serum levels of IL-6, TNF-α, IL-1β and MDA, and increased the level of GSH in CIA rats. A similar inhibitory effect was exhibited for Q11 in the AIA rats. Moreover, Q11 significantly impeded proliferation, migration, and invasion of human rheumatoid arthritis synovial fibroblasts cells. Q11 decreased the release of ROS and enhanced Nrf2 nuclear translocation and HO-1 expression in the cell nucleus. Overall, our results indicated that CYP2E1 may be a new target for RA and Q11 has potential protective effects against RA by reducing oxidative stress and opposing the inflammatory response via the ROS/Nrf2/HO-1 signaling pathway.

NRF2 Activation by Nitrogen Heterocycles: A Review

Several nitrogen heterocyclic analogues have been applied to clinical practice, and about 75% of drugs approved by the FDA contain at least a heterocyclic moiety. Thus, nitrogen heterocycles are beneficial scaffolds that occupy a central position in the development of new drugs. The fact that certain nitrogen heterocyclic compounds significantly activate the NRF2/ARE signaling pathway and upregulate the expression of NRF2-dependent genes, especially HO-1 and NQO1, underscores the need to study the roles and pharmacological effects of N-based heterocyclic moieties in NRF2 activation. Furthermore, nitrogen heterocycles exhibit significant antioxidant and anti-inflammatory activities. NRF2-activating molecules have been of tremendous research interest in recent times due to their therapeutic roles in neuroinflammation and oxidative stress-mediated diseases. A comprehensive review of the NRF2-inducing activities of N-based heterocycles and their derivatives will broaden their therapeutic prospects in a wide range of diseases. Thus, the present review, as the first of its kind, provides an overview of the roles and effects of nitrogen heterocyclic moieties in the activation of the NRF2 signaling pathway underpinning their antioxidant and anti-inflammatory actions in several diseases, their pharmacological properties and structural-activity relationship are also discussed with the aim of making new discoveries that will stimulate innovative research in this area.

PPARα agonist WY-14,643 induces adipose atrophy and fails to blunt chronic ethanol-induced hepatic fat accumulation in mice lacking adipose FGFR1

Fibroblast growth factor 21 (FGF21) is mainly regulated by peroxisome proliferator-activated receptor α (PPARα) in liver. The PPARα-FGF21 axis protects against alcohol-related liver disease (ALD). FGF21 exerts its effect via FGF receptor 1 (FGFR1). However, liver specific FGFR1 abrogation had no effect on ALD. Adipose tissues highly express FGFR1. When adipocyte specific FGFR1 knockout (fgfr1^adipoQ-cre) mice and corresponding normal control (fgfr1^fl/fl) mice were fed with Lieber-DeCarli ethanol liquid diet for 3 weeks, liver triglyceride (TG) accumulation was increased in the fgfr1^fl/fl mice to a greater extent than in the fgfr1^adipoQ-cre mice. When PPARα agonist WY-14,643 was added in the liquid ethanol diet at 10 mg/L, the ethanol-induced liver TG accumulation was blunted in the fgfr1^fl/fl mice but not in the fgfr1^adipoQ-cre mice. There was no significant difference in WY-14,643-induced fatty acid oxidation, ethanol metabolism, and oxidative stress between the fgfr1^fl/fl and fgfr1^adipoQ-cre mice. Interestingly, adipose atrophy was induced by WY-14,643 in the fgfr1^adipoQ-cre mice but not in the fgfr1^fl/fl mice. Serum free fatty acid was also decreased by WY-14,643 in the fgfr1^adipoQ-cre mice but not in the fgfr1^fl/fl mice. These results suggest that WY-14,643 inhibits alcoholic fatty liver and regulates adipose tissue mass and fat mobilization from adipose tissues to liver in an adipocyte FGFR1-dependent manner.

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

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

α-Lipoic acid protects against microcystin-LR induced hepatotoxicity through regeneration of glutathione via activation of Nrf2

Microcystins (MCs), as the most dominant bloom-forming strains in eutrophic surface water, can induce hepatotoxicity by oxidative stress. Alpha-lipoic acid (α-LA) is a super antioxidant that can induce the synthesis of antioxidants, such as glutathione (GSH), by nuclear factor erythroid 2-related factor 2 (Nrf2). However, the potential molecular mechanism of α-LA regeneration of GSH remains unclear. The present study aimed to investigate whether α-LA could reduce the toxicity of MCs induced in human hepatoma (HepG2), Bel7420 cells, and BALB/c mice by activating Nrf2 to regenerate GSH. Results showed that exposure to 10 μM microcystin-leucine arginine (MC-LR) reduced viability of HepG2 and Bel7402 cells and promoted the formation of reactive oxygen species (ROS) compared with untreated cells. Moreover, the protection of α-LA included reducing the level of ROS, increasing superoxide dismutase activity, and decreasing malondialdehyde. Levels of reduced glutathione (rGSH) and rGSH/oxidized glutathione were significantly increased in cells cotreated with α-LA and MC-LR compared to those treated with MC-LR alone, indicating an ability of α-LA to attenuate oxidative stress and MC-LR-induced cytotoxicity by increasing the amount of rGSH. α-LA can mediate GSH regeneration through the Nrf2 pathway under the action of glutathione reductase in MC-LR cell lines. Furthermore, the data also showed that α-LA-induced cytoprotection against MC-LR is associated with Nrf2 mediate pathway in vivo. These findings demonstrated the potential of α-LA to resist MC-LR-induced oxidative damage of liver.

Prominence of Oxidative Stress in the Management of Anti-tuberculosis Drugs Related Hepatotoxicity

Advanced medical services and treatments are available for treating Tuberculosis. Related prevalence has increased in recent times. Unfortunately, the continuous consumption of related drugs is also known for inducing hepatotoxicity which is a critical condition and cannot be overlooked. The present review article has focused on the pathways causing these toxicities and also the role of enzyme CYP2E1, hepatic glutathione, Nrf2-ARE signaling pathway, and Membrane Permeability Transition as possible targets which may help in preventing the hepatotoxicity induced by the drugs used in the treatment of tuberculosis.

Sagittaria sagittifolia polysaccharide protects against isoniazid- and rifampicin-induced hepatic injury via activation of nuclear factor E2-related factor 2 signaling in mice

ETHNOPHARMACOLOGICAL RELEVANCE

The Sagittaria sagittifolia L. polysaccharide (SSP) is a purified form of a homogeneous polysaccharide isolated from the root tubers of S. sagittifolia, which has been used as a protectant against hepatotoxicity induced by coadministration of isoniazid and rifampicin. However, the protective effect of SSP against isoniazid- and rifampicin-induced liver injury has never been studied.

AIM OF THE STUDY

In this study, the hepatoprotective effect of SSP and its underlying mechanism were investigated in mice with isoniazid- and rifampicin-induced liver injury.

MATERIALS AND METHODS

Liver injury was induced in mice by intragastric administration of isoniazid and rifampicin, and the mice were divided into the following six groups: standard control (administration of saline by gavage), model (intragastric administration of isoniazid and rifampicin at 100 mg/kg/day each), positive control (100 mg/kg/day silymarin by gavage 4 h after isoniazid and rifampicin administration), and SSP-treated (200, 400, or 800 mg/kg/day SSP by gavage after isoniazid and rifampicin administration). Subsequently, blood and liver samples were collected from all the animals and were assessed.

RESULTS

SSP significantly alleviated the liver injury, as evidenced by decreased activities of alanine aminotransferase, aspartate aminotransferase, and lactate dehydrogenase in the serum and a decreased level of malondialdehyde in the liver, as well as by an increased level of glutathione and increased activities of superoxide dismutase and catalase in the liver. SSP also effectively reduced the pathological tissue damage. The gene and protein expression of cytochrome P450 (CYP) 2E1 and CYP3A4 was inhibited by SSP. The gene and protein expression of nuclear factor erythroid 2-related factor 2 (NRF2), glutamate-cysteine ligase, and heme oxygenase-1 were induced by SSP, whereas that of Kelch-like ECH-associated protein 1 was inhibited.

CONCLUSIONS

SSP exerts a protective effect against isoniazid- and rifampicin-induced liver injury in mice. The underlying mechanisms may involve activation of NRF2 and its target antioxidant enzymes and inhibition of the expression of CYPs.

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.

Alcoholic fatty liver is enhanced in CYP2A5 knockout mice: The role of the PPARα-FGF21 axis

BACKGROUND & AIMS

Cytochrome P450 2A5 (CYP2A5) is induced by ethanol, and the ethanol induction of CYP2A5 is regulated by nuclear factor-erythroid 2-related factor 2 (NRF2). Cyp2a5 knockout (Cyp2a5^-/-) mice develop more severe alcoholic fatty liver than Cyp2a5^+/+ mice. Fibroblast growth factor 21 (FGF21), a PPARα-regulated liver hormone, is involved in hepatic lipid metabolism. Alcoholic and non-alcoholic fatty liver are enhanced in Pparα knockout (Pparα^-/-) mice. This study investigates the relationship between the PPARα-FGF21 axis and the enhanced alcoholic fatty liver in Cyp2a5^-/- mice.

METHODS

Mice were fed the Lieber-Decarli ethanol diet to induce alcoholic fatty liver.

RESULTS

More severe alcoholic fatty liver disease was developed in Cyp2a5^-/- mice than in Cyp2a5^+/+ mice. Basal FGF21 levels were higher in Cyp2a5^-/- mice than in Cyp2a5^+/+ mice, but ethanol did not further increase the elevated FGF21 levels in Cyp2a5^-/- mice while FGF21 was induced by ethanol in Cyp2a5^+/+ mice. Basal levels of serum FGF21 were lower in Pparα^-/- mice than in Pparα^+/+ mice; ethanol induced FGF21 in Pparα^+/+ mice but not in Pparα^-/- mice, whereas ethanol induced hypertriglyceridemia in Pparα^-/- mice but not in Pparα^+/+ mice. Administration of recombinant FGF21 normalized serum FGF21 and triglyceride in Pparα^-/- mice. Alcoholic fatty liver was enhanced in liver-specific Fgf21 knockout mice. Pparα and Cyp2a5 double knockout (Pparα^-/-/Cyp2a5^-/-) mice developed more severe alcoholic fatty liver than Pparα^+/+/Cyp2a5^-/- mice.

CONCLUSIONS

These results suggest that CYP2A5 protects against the development of alcoholic fatty liver disease, and the PPARα-FGF21 axis contributes to the protective effects of CYP2A5 on alcoholic fatty liver disease.

Alcoholic Liver Disease: from CYP2E1 to CYP2A5

This article reviews recent studies on CYP2E1-mediated alcoholic liver injury, the induction of CYP2A5 by alcohol and the mechanism for this upregulation, especially the permissive role of CYP2E1 in the induction of CYP2A5 by alcohol and the CYP2E1-ROS-Nrf2 pathway, and protective effects of CYP2A5 against ethanol-induced oxidative liver injury. Ethanol can induce CYP2E1, an active generator of reactive oxygen species (ROS), and CYP2E1 is a contributing factor for alcoholinduced oxidative liver injury. CYP2A5, another isoform of cytochrome P450, can also be induced by ethanol. Chronic feeding of ethanol to wild type mice increased CYP2A5 catalytic activity, protein and mRNA levels as compared to pair-fed controls. This induction was blunted in CYP2E1 knockout (cyp2e1-/-) mice but was restored when human CYP2E1 was reintroduced and expressed in cyp2e1-/- mice. Ethanol-induced CYP2E1 co-localized with CYP2A5 and preceded the elevation of CYP2A5. The antioxidants N-acetyl cysteine and vitamin C lowered the alcohol elevation of ROS and blunted the alcohol induction of CYP2A5, but not CYP2E1, suggesting ROS play a novel role in the crosstalk between CYP2E1 and CYP2A5. The antioxidants blocked the activation of Nrf2, a transcription factor known to upregulate expression of CYP2A5. When alcohol-induced liver injury was enhanced in Nrf2 knockout (Nrf2-/-) mice, alcohol elevation of CYP2A5 but not CYP2E1 was also lower in Nrf2-/- mice. CYP2A5 knockout (cyp2a5-/-) mice exhibited an enhanced alcoholic liver injury compared with WT mice as indicated by serum ALT, steatosis and necroinflammation. Alcohol-induced hyperglycemia were observed in cyp2a5-/- mice but not in WT mice.

Reversal of ethanol-induced hepatotoxicity by cinnamic and syringic acids in mice

Ethanol was used to induce acute hepatotoxicity in mice. Effects of cinnamic acid (CA) and syringic acid (SA) post-intake for hepatic recovery from alcoholic injury was investigated. Ethanol treated mice were supplied by CA or SA at 40 or 80 mg/kg BW/day for 5 days. Results showed that ethanol stimulated protein expression of CYP2E1, p47^phox, gp91^phox, cyclooxygenase-2 and nuclear factor kappa B in liver. CA or SA post-intake restricted hepatic expression of these molecules. Ethanol suppressed nuclear factor erythroid 2-related factor (Nrf2) expression, and CA or SA enhanced Nrf2 expression in cytosolic and nuclear fractions. Ethanol increased the release of reactive oxygen species, oxidized glutathione, interleukin-6, tumor necrosis factor-alpha, nitric acid and prostaglandin E₂. CA or SA lowered hepatic production of these oxidative and inflammatory factors. Histological data revealed that ethanol administration caused obvious foci of inflammatory cell infiltration, and CA or SA post-intake improved hepatic inflammatory infiltration. These findings support that cinnamic acid and syringic acid are potent nutraceutical agents for acute alcoholic liver disease therapy. However, potential additive or synergistic benefits of cinnamic and syringic acids against ethanol-induced hepatotoxicity need to be investigated.

Toxicogenomics Case Study: Furan

Development of pragmatic methodologies for human health risk assessment is required to address current regulatory challenges. We applied three toxicogenomic approaches—quantitative, predictive, and mechanistic—to a case study in mice exposed for 3 weeks to the hepatocarcinogen furan. We modeled the dose response of a variety of transcriptional endpoints and found that they produced benchmark doses similar to the furan-dependent cancer benchmark doses. Meta-analyses showed strong similarity between furan-dependent gene expression changes and those associated with several hepatic pathologies. Molecular pathways facilitated the development of a molecular mode of action for furan-induced hepatocellular carcinogenicity. Finally, we compared transcriptomic profiles derived from formalin-fixed and paraffin-embedded (FFPE) samples with those from high-quality frozen samples to evaluate whether archival samples are a viable option for toxicogenomic studies. The advantage of using FFPE tissues is that they are very well characterized (phenotypically); the disadvantage is that formalin degrades biomacromolecules, including RNA. We found that FFPE samples can be used for toxicogenomics using a ribo-depletion RNA-seq protocol. Our case study demonstrates the utility of toxicogenomics data to human health risk assessment, the potential of archival FFPE tissue samples, and identifies viable strategies toward the reduction of animal usage in chemical testing.

Chronic Glutathione Depletion Confers Protection against Alcohol-induced Steatosis: Implication for Redox Activation of AMP-activated Protein Kinase Pathway

The pathogenesis of alcoholic liver disease (ALD) is not well established. However, oxidative stress and associated decreases in levels of glutathione (GSH) are known to play a central role in ALD. The present study examines the effect of GSH deficiency on alcohol-induced liver steatosis in Gclm knockout (KO) mice that constitutively have ≈15% normal hepatic levels of GSH. Following chronic (6 week) feeding with an ethanol-containing liquid diet, the Gclm KO mice were unexpectedly found to be protected against steatosis despite showing increased oxidative stress (as reflected in elevated levels of CYP2E1 and protein carbonyls). Gclm KO mice also exhibit constitutive activation of liver AMP-activated protein kinase (AMPK) pathway and nuclear factor-erythroid 2–related factor 2 target genes, and show enhanced ethanol clearance, altered hepatic lipid profiles in favor of increased levels of polyunsaturated fatty acids and concordant changes in expression of genes associated with lipogenesis and fatty acid oxidation. In summary, our data implicate a novel mechanism protecting against liver steatosis via an oxidative stress adaptive response that activates the AMPK pathway. We propose redox activation of the AMPK may represent a new therapeutic strategy for preventing ALD.

Gender differences in murine pulmonary responses elicited by cellulose nanocrystals

Background

Cellulose-based materials have been used for centuries to manufacture different goods derived from forestry and agricultural sources. In the growing field of nanocellulose applications, its uniquely engineered properties are instrumental for inventive products coming to competitive markets. Due to their high aspect ratio and stiffness, it is speculated that cellulose nanocrystals (CNC) may cause similar pulmonary toxicity as carbon nanotubes and asbestos, thus posing a potential negative impact on public health and the environment.

Methods

The present study was undertaken to investigate the pulmonary outcomes induced by repeated exposure to respirable CNC. C57BL/6 female and male mice were exposed by pharyngeal aspiration to CNC (40 μg/mouse) 2 times a week for 3 weeks. Several biochemical endpoints and pathophysiological outcomes along with gene expression changes were evaluated and compared in the lungs of male and female mice.

Results

Exposure to respirable CNC caused pulmonary inflammation and damage, induced oxidative stress, elevated TGF-β and collagen levels in lung, and impaired pulmonary functions. Notably, these effects were markedly more pronounced in females compared to male mice. Moreover, sex differences in responses to pulmonary exposure to CNC were also detected at the level of global mRNA expression as well as in inflammatory cytokine/chemokine activity.

Conclusions

Overall, our results indicate that there are considerable differences in responses to respirable CNC based on gender with a higher pulmonary toxicity observed in female mice.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-016-0140-x) contains supplementary material, which is available to authorized users.

N-acetylcysteine inhibits the up-regulation of mitochondrial biogenesis genes in livers from rats fed ethanol chronically

BACKGROUND

Chronic ethanol (EtOH) administration to experimental animals induces hepatic oxidative stress and up-regulates mitochondrial biogenesis. The mechanisms by which chronic EtOH up-regulates mitochondrial biogenesis have not been fully explored. In this work, we hypothesized that oxidative stress is a factor that triggers mitochondrial biogenesis after chronic EtOH feeding. If our hypothesis is correct, co-administration of antioxidants should prevent up-regulation of mitochondrial biogenesis genes.

METHODS

Rats were fed an EtOH-containing diet intragastrically by total enteral nutrition for 150 days, in the absence or presence of the antioxidant N-acetylcysteine (NAC) at 1.7 g/kg/d; control rats were administered isocaloric diets where carbohydrates substituted for EtOH calories.

RESULTS

EtOH administration significantly increased hepatic oxidative stress, evidenced as decreased liver total glutathione and reduced glutathione/glutathione disulfide ratio. These effects were inhibited by co-administration of EtOH and NAC. Chronic EtOH increased the expression of mitochondrial biogenesis genes including peroxisome proliferator-activated receptor gamma-coactivator-1 alpha and mitochondrial transcription factor A, and mitochondrial DNA; co-administration of EtOH and NAC prevented these effects. Chronic EtOH administration was associated with decreased mitochondrial mass, inactivation and depletion of mitochondrial complex I and complex IV, and increased hepatic mitochondrial oxidative damage, effects that were not prevented by NAC.

CONCLUSIONS

These results suggest that oxidative stress caused by chronic EtOH triggered the up-regulation of mitochondrial biogenesis genes in rat liver, because an antioxidant such as NAC prevented both effects. Because NAC did not prevent liver mitochondrial oxidative damage, extra-mitochondrial effects of reactive oxygen species may regulate mitochondrial biogenesis. In spite of the induction of hepatic mitochondrial biogenesis genes by chronic EtOH, mitochondrial mass and function decreased probably in association with mitochondrial oxidative damage. These results also predict that the effectiveness of NAC as an antioxidant therapy for chronic alcoholism will be limited by its limited antioxidant effects in mitochondria, and its inhibitory effect on mitochondrial biogenesis.

The role of CYP2A5 in liver injury and fibrosis: chemical-specific difference

Liver injuries induced by carbon tetrachloride (CCL4) or thioacetamide (TAA) are dependent on cytochrome P450 2E1 (CYP2E1). CYP2A5 can be induced by TAA but not by CCL4. In this study, liver injury including fibrosis induced by CCL4 or TAA were investigated in wild-type (WT) mice and CYP2A5 knockout (cyp2a5 (-/-) ) mice as well as in CYP2E1 knockout (cyp2e1 (-/-) ) mice as a comparison. Acute and subchronic liver injuries including fibrosis were induced by CCL4 and TAA in WT mice but not in cyp2e1 (-/-) mice, confirming the indispensable role of CYP2E1 in CCL4 and TAA hepatotoxicity. WT mice and cyp2a5 (-/-) mice developed comparable acute liver injury induced by a single injection of CCL4 as well as subchronic liver injury including fibrosis induced by 1 month of repeated administration of CCL4, suggesting that CYP2A5 does not affect CCL4-induced liver injury and fibrosis. However, while 200 mg/kg TAA-induced acute liver injury was comparable in WT mice and cyp2a5 (-/-) mice, 75 and 100 mg/kg TAA-induced liver injury were more severe in cyp2a5 (-/-) mice than those found in WT mice. After multiple injections with 200 mg/kg TAA for 1 month, while subchronic liver injury as indicated by serum aminotransferases was comparable in WT mice and cyp2a5 (-/-) mice, liver fibrosis was more severe in cyp2a5 (-/-) mice than that found in WT mice. These results suggest that while both CCL4- and TAA-induced liver injuries and fibrosis are CYP2E1 dependent, under some conditions, CYP2A5 may protect against TAA-induced liver injury and fibrosis, but it does not affect CCL4 hepatotoxicity.

GET73 Prevents Ethanol-Induced Neurotoxicity in Primary Cultures of Rat Hippocampal Neurons

AIMS

N-[(4-trifluoromethyl) benzyl] 4-methoxybutyramide (GET73) may be considered a promising therapeutic agent for the treatment of alcohol use disorders. The compound displayed anti-alcohol and anxiolytic properties in rat. In the present study, an in vitro experimental model of chronic ethanol treatment was used to investigate the ability of the compound to counteract the ethanol-induced neurotoxicity.

METHODS

Primary cultures of rat hippocampal neurons were exposed to ethanol (75 mM; 4 days) and the neuroprotective effects of GET73 were assessed by evaluating cell viability, cell morphology, glutamate levels and reactive oxygen species production.

RESULTS

The exposure to ethanol induced a reduction of cell viability, an alteration of cytoskeleton, a decrease in extracellular glutamate levels and an increase of reactive oxygen species production. The addiction of GET73 (1 and 10 µM) 1 h before and during chronic ethanol exposure prevented all the above ethanol-induced effects. Based on the proposed GET73 mechanism of action, the effects of mGlu5 receptor negative allosteric modulator, 2-methyl-6-(phenylethynyl)-pyridine (MPEP), on ethanol-induced reduction of cell viability were also assessed. The results indicated that the addiction of MPEP (100 µM) 1 h before and during chronic ethanol exposure prevented the ethanol-induced cell viability reduction.

CONCLUSION

The present findings provide the first evidence that GET73 shows a neuroprotective role against ethanol-induced neurotoxicity in primary cultures of rat hippocampal neurons. Together with previous findings, these results suggest that GET73 possesses multifaceted properties thus lending further support to the significance of developing GET73 as a therapeutic tool for use in the treatment of alcohol use disorders.

Isoniazid prevents Nrf2 translocation by inhibiting ERK1 phosphorylation and induces oxidative stress and apoptosis

Isoniazid is used either alone or in combination with other drugs for the treatment of tuberculosis. It is also used for the prevention of tuberculosis. Chronic treatment of Isoniazid may cause severe liver damage leading to acute liver failure. The mechanism through which Isoniazid causes liver damage is investigated. Isoniazid treatment generates reactive oxygen species and induces apoptosis in Hep3B cells. It induces antioxidative and apoptotic genes leading to increase in mRNA expression and protein levels in Hep3B cells. Whole genome expression analysis of Hep3B cells treated with Isoniazid has resulted in differential expression of various genes playing prime role in regulation of apoptotic, antioxidative, DNA damage, cell signaling, cell proliferation and differentiation pathways. Isoniazid increased cytosolic Nrf2 protein level while decreased nuclear Nrf2 protein level. It also decreased ERK1 phosphorylation and treatment of Hep3B cells with ERK inhibitor followed by Isoniazid resulting in increased apoptosis in these cells. Two dimensional gel electrophoresis results have also shown differential expression of various protein species including heat shock proteins, proteins playing important role in oxidative stress, DNA damage, apoptosis, cell proliferation and differentiation. Results suggest that Isoniazid induces apoptosis through oxidative stress and also prevents Nrf2 translocation into the nucleus by reducing ERK1 phosphorylation thus preventing cytoprotective effect.

Antagonistic effects of acetylshikonin on LPS-induced NO and PGE2 production in BV2 microglial cells via inhibition of ROS/PI3K/Akt-mediated NF-κB signaling and activation of Nrf2-dependent HO-1

Although acetylshikonin (ACS) is known to have antioxidant and antitumor activities, whether ACS regulates the expression of proinflammatory mediators in lipopolysaccharide (LPS)-stimulated microglial cells remains unclear. In this study, it was found that ACS isolated from Lithospermum erythrorhizon inhibits LPS-induced nitric oxide (NO) and prostaglandin E2 (PGE2) release by suppressing the expression of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) in BV2 microglial cells. Furthermore, ACS reduced the LPS-induced DNA-binding activity of nuclear factor-κB (NF-κB) and subsequently suppressed iNOS and COX-2 expression. Consistent with these data, ACS attenuated the phosphorylation of PI3K and Akt and suppressed the DNA-binding activity of NF-κB by inducing the generation of reactive oxygen species (ROS) in LPS-stimulated cells. In addition, ACS enhanced heme oxygenase-1 (HO-1) expression via nuclear factor-erythroid 2-related factor 2 (Nrf2) activation. Zinc protoporphyrin, a specific HO-1 inhibitor, partially attenuated the antagonistic effects of ACS on LPS-induced NO and PGE2 production. By contrast, the presence of cobalt protoporphyrin, a specific HO-1 inducer, potently suppressed LPS-induced NO and PGE2 production. These data indicate that ACS downregulates proinflammatory mediators such as NO and PGE2 by suppressing PI3K/Akt-dependent NF-κB activity induced by ROS as well as inducing Nrf2-dependent HO-1 activity. Taken together, ACS might be a good candidate to regulate LPS-mediated inflammatory diseases.

Absence of cytochrome P450 2A5 enhances alcohol-induced liver injury in mice

BACKGROUND

Ethanol can induce cytochrome P450 2E1, an active generator of reactive oxygen species, and this cytochrome is considered a risk factor for oxidative liver injury. Recently, we found that in addition to P450 2E1 also cytochrome P450 2A5, another isoform of cytochrome P450, can be induced by ethanol, and that ethanol induction of cytochrome P450 2A5 is P450 2E1-dependent.

AIMS

To investigate the role of cytochrome P450 2A5 in alcohol-induced liver injury.

METHODS

Cytochrome P450 2A5-knockout mice and wild type mice were fed the Lieber-Decarli ethanol liquid diet to induce liver injury. Controls were fed the Lieber-Decarli control diet.

RESULTS

After 4 weeks of feeding with Lieber-Decarli diet, ethanol-induced liver injury was enhanced in the knockout mice compared with wild type mice, as indicated by serum transaminases, hepatic fat accumulation (steatosis), and necroinflammation observed in liver sections with Haematoxylin & Eosin staining. Ethanol-induced oxidative stress was also higher in the knockout mice than the wild types. Ethanol feeding induced cytochrome P450 2A5 in wild type mice but not in the knockout mice, while induction of cytochrome P450 2E1 was comparable in the knockout and wild type mice.

CONCLUSION

These results suggest that cytochrome P450 2A5 protects against ethanol-induced oxidative liver injury.

Matching Diabetes and Alcoholism: Oxidative Stress, Inflammation, and Neurogenesis Are Commonly Involved

Diabetes and alcohol misuse are two of the major challenges in health systems worldwide. These two diseases finally affect several organs and systems including the central nervous system. Hippocampus is one of the most relevant structures due to neurogenesis and memory-related processing among other functions. The present review focuses on the common profile of diabetes and ethanol exposure in terms of oxidative stress and proinflammatory and prosurvival recruiting transcription factors affecting hippocampal neurogenesis. Some aspects around antioxidant strategies are also included. As a global conclusion, the present review points out some common hits on both diseases giving support to the relations between alcohol intake and diabetes.

1,2-Dichloroethane induced nephrotoxicity through ROS mediated apoptosis in vitro and in vivo

1,2-Dichloroethane (DCE) decreased kidney cell proliferation, even induced cell apoptosisviaincreasing the generation of ROS in the presence of an extra-metabolic system.

Inhibition of cytochrome P450 2E1 and activation of transcription factor Nrf2 are renoprotective in myoglobinuric acute kidney injury

Rhabdomyolysis accounts for ∼10% of acute kidney injuries. In glycerol-induced myoglobinuric acute kidney injury, we found an increase in the nuclear factor erythroid 2-related factor 2 (Nrf2) nuclear protein, a key redox-sensitive transcription factor, and Nrf2-regulated genes and proteins including upregulation of heme oxygenase-1. In in vitro studies, pretreatment of LLC-PK1 cells with an activator of Nrf2 before myoglobin exposure significantly decreased oxidant generation and cytotoxicity, whereas Nrf2 inhibition and gene silencing exacerbated the injury. Chlormethiazole, a specific CYP2E1 transcription inhibitor, prevented an increase in catalytic iron in the kidneys, decreased oxidative stress, blocked nuclear translocation of the Nrf2 protein, decreased heme oxygenase-1 upregulation, and provided functional and histological protection against acute kidney injury. CYP2E1 inhibitors and gene silencing in renal tubular epithelial cells significantly decreased reactive oxygen species generation and provided marked protection against myoglobin-induced cytotoxicity. Thus, during CYP2E1-induced oxidative stress, the transcription factor Nrf2 has a pivotal role in the early adaptive response. Inhibition of CYP2E1 coupled with the prior induction of Nrf2 may be a valuable tool to reduce CYP2E1-mediated rhabdomyolysis-induced acute kidney injury.

Anti-inflammatory effects of β-hydroxyisovalerylshikonin in BV2 microglia are mediated through suppression of the PI3K/Akt/NF-kB pathway and activation of the Nrf2/HO-1 pathway

In the present study, we investigated whether β-hydroxyisovalerylshikonin (β-HIVS) affects the production of proinflammatory mediators such as nitric oxide (NO) and prostaglandin E2 (PGE2) in BV2 microglial cells. Our data showed that β-HIVS inhibited secretion of NO and PGE2 and downregulated expression of their main regulatory genes, inducible NO synthesis (iNOS) and cyclooxygenase-2 (COX-2). β-HIVS also reduced the LPS-induced DNA-binding activity of nuclear factor-κB (NF-κB) by suppressing nuclear translocation of the NF-κB subunits and inhibiting the degradation and phosphorylation of IκBα. Furthermore, an NF-κB inhibitor, pyrrolidine dithiocarbamate (PDTC), attenuated LPS-stimulated iNOS and COX-2 expression, suggesting that NF-κB inhibition is a main effector in the expression of iNOS and COX-2. We also found that LPS-induced NF-κB activation is regulated through inhibition of PI3K/Akt phosphorylation in response to β-HIVS. Additionally, β-HIVS caused the induction of heme oxygenase-1 (HO-1) via upregulation of nuclear factor-erythroid 2-related factor 2 (Nrf2), both of which are involved in the secretion of proinflammatory mediators such as NO and PGE2. Taken together, our data indicate that β-HIVS diminishes the proinflammatory mediators NO and PGE2 and the expression of their regulatory genes, iNOS and COX-2, in LPS-stimulated BV2 microglial cells by inhibiting PI3K/Akt-dependent NF-κB activation and inducing Nrf2-mediated HO-1 expression.

Cytochrome P450 2E1 (CYP2E1) regulates the response to oxidative stress and migration of breast cancer cells

Introduction

The cytochrome P450 (CYP) enzymes are a class of heme-containing enzymes involved in phase I metabolism of a large number of xenobiotics. The CYP family member CYP2E1 metabolises many xenobiotics and pro-carcinogens, it is not just expressed in the liver but also in many other tissues such as the kidney, the lung, the brain, the gastrointestinal tract and the breast tissue. It is induced in several pathological conditions including cancer, obesity, and type II diabetes implying that this enzyme is implicated in other biological processes beyond its role in phase I metabolism. Despite the detailed description of the role of CYP2E1 in the liver, its functions in other tissues have not been extensively studied. In this study, we investigated the functional significance of CYP2E1 in breast carcinogenesis.

Methods

Cellular levels of reactive oxygen species (ROS) were measured by H₂DCFDA (2 2.9.2 2′,7′-dichlorodihydrofluorescein diacetate) staining and autophagy was assessed by tracing the cellular levels of autophagy markers using western blot assays. The endoplasmic reticulum stress and the unfolded protein response (UPR) were detected by luciferase assays reflecting the splicing of mRNA encoding the X-box binding protein 1 (XBP1) transcription factor and cell migration was evaluated using the scratch wound assay. Gene expression was recorded with standard transcription assays including luciferase reporter and chromatin immunoprecipitation.

Results

Ectopic expression of CYP2E1 induced ROS generation, affected autophagy, stimulated endoplasmic reticulum stress and inhibited migration in breast cancer cells with different metastatic potential and p53 status. Furthermore, evidence is presented indicating that CYP2E1 gene expression is under the transcriptional control of the p53 tumor suppressor.

Conclusions

These results support the notion that CYP2E1 exerts an important role in mammary carcinogenesis, provide a potential link between ethanol metabolism and breast cancer and suggest that progression, and metastasis, of advanced stages of breast cancer can be modulated by induction of CYP2E1 activity.

Protective effects of metallothionein on isoniazid and rifampicin-induced hepatotoxicity in mice

Isoniazid (INH) and Rifampicin (RFP) are widely used in the world for the treatment of tuberculosis, but the hepatotoxicity is a major concern during clinical therapy. Previous studies showed that these drugs induced oxidative stress in liver, and several antioxidants abated this effect. Metallothionein (MT), a member of cysteine-rich protein, has been proposed as a potent antioxidant. This study attempts to determine whether endogenous expression of MT protects against INH and RFP-induced hepatic oxidative stress in mice. Wild type (MT+/+) and MT-null (MT−/−) mice were treated intragastrically with INH (150 mg/kg), RFP (300 mg/kg), or the combination (150 mg/kg INH +300 mg/kg RFP) for 21 days. The results showed that MT−/− mice were more sensitive than MT+/+ mice to INH and RFP-induced hepatic injuries as evidenced by hepatic histopathological alterations, increased serum AST levels and liver index, and hepatic oxidative stress as evidenced by the increase of MDA production and the change of liver antioxidant status. Furthermore, INH increased the protein expression of hepatic CYP2E1 and INH/RFP (alone or in combination) decreased the expression of hepatic CYP1A2. These findings clearly demonstrate that basal MT provides protection against INH and RFP-induced toxicity in hepatocytes. The CYP2E1 and CYP1A2 were involved in the pathogenesis of INH and RFP-induced hepatotoxicity.

Cytochrome P450 system as potential biomarkers of certain toxicants: comparison between plant and animal models

In present study, we measured the activities of some selected cytochrome P450 isozymes like ethoxyresorufin-o-deethylase (EROD), pentoxyresorufin-o-deethylase (PROD), and N-nitrosodimethylamine demethylase (NDMA-d) treating experimental rats with different environmental toxicants, namely trichloroethylene (TCE), heavy metal mixture, and ethyl alcohol individually or in combination and by exposing the Allium cepa bulbs to increasing concentration of TCE for 48 h. In animal system, NDMA-d activity displayed a remarkable amplification by 4.2-fold in the liver of alcohol ingested rats compared with control animals. TCE intake also resulted in a marked increase of around 3.8-fold and 1.2-fold in rats' NDMA-d activity in the liver and kidney, respectively. In onion bulbs, an amazing rise in the activity of test enzymes was recorded in a dose-dependent manner. Among the said enzymes, PROD showed maximum increase up to the extent of 22-fold in comparison with control at 20 ppm of TCE exposure, whereas NDMA-d and EROD showed 11- and 9-fold increase in enzymatic activity, respectively, compared with the control. Based on this study, we conclude and advocate that all the selected isozymes of CYP450 system, viz. PROD, NDMA-d, and EROD can act as potent biomarkers in plant system for assessing the TCE pollution.

Regulation of cytochrome P450 2e1 expression by ethanol: role of oxidative stress-mediated pkc/jnk/sp1 pathway

CYP2E1 metabolizes ethanol leading to production of reactive oxygen species (ROS) and acetaldehyde, which are known to cause not only liver damage but also toxicity to other organs. However, the signaling pathways involved in CYP2E1 regulation by ethanol are not clear, especially in extra-hepatic cells. This study was designed to examine the role of CYP2E1 in ethanol-mediated oxidative stress and cytotoxicity, as well as signaling pathways by which ethanol regulates CYP2E1 in extra-hepatic cells. In this study, we used astrocytic and monocytic cell lines, because they are important cells in central nervous system . Our results showed that 100 mM ethanol significantly induced oxidative stress, apoptosis, and cell death at 24 h in the SVGA astrocytic cell line, which was rescued by a CYP2E1 selective inhibitor, diallyl sulfide (DAS), CYP2E1 siRNA, and antioxidants (vitamins C and E). Further, we showed that DAS and vitamin C abrogated ethanol-mediated (50 mℳ) induction of CYP2E1 at 6 h, as well as production of ROS at 2 h, suggesting the role of oxidative stress in ethanol-mediated induction of CYP2E1. We then investigated the role of the protein kinase C/c-Jun N-terminal kinase/specificity protein1 (PKC/JNK/SP1) pathway in oxidative stress-mediated CYP2E1 induction. Our results showed that staurosporine, a non-specific inhibitor of PKC, as well as specific PKCζ inhibitor and PKCζ siRNA, abolished ethanol-induced CYP2E1 expression. In addition, inhibitors of JNK (SP600125) and SP1 (mithramycin A) completely abrogated induction of CYP2E1 by ethanol in SVGA astrocytes. Subsequently, we showed that CYP2E1 is also responsible for ethanol-mediated oxidative stress and apoptotic cell death in U937 monocytic cell lines. Finally, our results showed that PKC/JNK/SP1 pathway is also involved in regulation of CYP2E1 in U937 cells. This study has clinical implications with respect to alcohol-associated neuroinflammatory toxicity among alcohol users.

Exploring the mechanisms of alcohol-related damage in oral mucosa - is oxidative stress associated with the increase in cell proliferation in rat tongue epithelium?

CONTEXT

Alcohol consumption has been related to a cell proliferation increase in oral epithelium but its mechanism remains unclear.

OBJECTIVE

The aim of this study was to investigate whether oxidative stress parameters are implicated in the induction of cell proliferation in rat tongue epithelium after different times of chronic alcohol consumption.

MATERIALS AND METHODS

Cell proliferation was assessed in tongue epithelium using AgNOR (argyrophilic proteins related to active nucleolar organizer regions) quantification. Oxidative stress parameters [lipid peroxidation, protein carbonyls, superoxide dismutase activity and catalase (CAT) activity and immunocontent] and Nrf2 immunocontent were quantified in tongue homogenates.

RESULTS AND DISCUSSION

Mean AgNOR numbers (mAgNOR) per nucleus was 2.22 ± 0.30 in ventral tongue epithelium after 120 days of alcohol consumption (vs. 1.87 ± 0.18 for control animals and 1.91 ± 0.23 for animals treated with alcohol for 60 days) indicating cell proliferation increase (p < 0.05, ANOVA followed by Tukey post hoc). Interestingly, 60 days of alcohol consumption induced changes in oxidative stress parameters, but no alteration in cell proliferation. Vitamin E co-treatment was conduced in order to evaluate its possible protective effects. The 120 day Tween + vitamin E + alcohol treatment induced an increase in mAgNORs when compared to the Tween + vitamin E treated group (respectively 2.10 ± 0.30 vs. 1.77 ± 0.11, p < 0.05, ANOVA followed by Tukey post hoc), showing that vitamin E co-treatment had no protective effects. In addition, an inverse association was observed between CAT activity and AgNORs quantity (R = -0.32; p < 0.05, Person's correlation) as well as the possible involvement of Nrf2 in alcohol-related damage.

CONCLUSIONS

Our findings suggest that the increase in cell proliferation associated with alcohol-related damage has no direct relation with an imbalance in oxidative parameters. In contrast, our results indicate that hydrogen peroxide may be implicated in cellular signaling during proliferation in the oral mucosa.

Alcohol steatosis and cytotoxicity: the role of cytochrome P4502E1 and autophagy

The goal of the current study was to evaluate whether CYP2E1 plays a role in binge-ethanol induced steatosis and if autophagy impacts CYP2E1-mediated hepatotoxicity, oxidative stress and fatty liver formation produced by ethanol. Wild type (WT), CYP2E1 knockin (KI) and CYP2E1 knockout (KO) mice were gavaged with 3g/kg body wt ethanol twice a day for four days. This treatment caused fatty liver, elevation of CYP2E1 and oxidative stress in WT and KI mice but not KO mice. Autophagy was impaired in ethanol-treated KI mice compared to KO mice as reflected by a decline in the LC3-II/LC3-I ratio and lower total LC-3 and Beclin-1 levels coupled to increases in P62, pAKT/AKT and mTOR. Inhibition of macroautophagy by administration of 3-methyladenine enhanced the binge ethanol hepatotoxicity, steatosis and oxidant stress in CYP2E1 KI, but not CYP2E1 KO mice. Stimulation of autophagy by rapamycin blunted the elevated steatosis produced by binge ethanol. Treatment of HepG2 E47 cells which express CYP2E1 with 100mM ethanol for 8 days increased fat accumulation and oxidant stress but decreased autophagy. Ethanol had no effect on these reactions in HepG2 C34 cells which do not express CYP2E1. Inhibition of autophagy elevated ethanol toxicity, lipid accumulation and oxidant stress in the E47, but not C34 cells. The antioxidant N-acetylcysteine, and CYP2E1 inhibitor chlormethiazole blunted these effects of ethanol. These results indicate that CYP2E1 plays an important role in binge ethanol-induced fatty liver. We propose that CYP2E1-derived reactive oxygen species inhibit autophagy, which subsequently causes accumulation of lipid droplets. Inhibition of autophagy promotes binge ethanol induced hepatotoxicity, steatosis and oxidant stress via CYP2E1.

Nrf2: friend and foe in preventing cigarette smoking-dependent lung disease

Chronic exposure to cigarette smoke (CS) generally confronts cellular defense systems with one of the strongest known environmental challenges. In particular, the continuous exposure of tissues of the respiratory tract to abundant concentrations of radicals; volatile compounds of the gas phase, mainly reactive oxygen and nitrogen species; and CS condensate deposits trigger a pleiotropic adaptive response, generally aimed at restoring tissue homeostasis. As documented by numerous studies published over the past decade, a hallmark of this defense system is the activation of the transcription factor NF-E2-related factor 2 (Nrf2), which, consequent to its established role as master regulator of the cellular antioxidant response, has been shown to orchestrate the first line of defense against cell- and tissue-damaging components present in CS. The key to CS-dependent Nrf2 activation is assumed to be based on the long-known phenomenon of a general strong sulfhydryl (-SH) reactivity inherent to CS. This chemical trait is virtually predestined to be sensitized by the major route leading to Nrf2 activation, characterized by its dependence on the interaction of electrophiles with specific cysteine residues inherited by Nrf2's negative cytosolic regulator Keap1 (Kelch-like ECH-associated protein 1). In addition, other pathways involving CS-activated protein kinases implicated in the upstream regulation of Nrf2, such as protein kinase C, represent an alternative/complementary mechanism of CS-induced Nrf2 activation. Because of the outstanding function of the Nrf2-Keap1 axis in defending cells and tissues against oxidant and chemical stress, either directly or indirectly via cross-talking with other defense pathways, changes in the Nrf2 or Keap1 genotype have long been associated with disease development. In terms of the two major smoking-related diseases of the lung, that is, emphysema and lung cancer, a fully functional Nrf2 genotype seems to be necessary, although not sufficient by itself, to protect the smoker from acquiring emphysema. Contrasting with this protective role, however, Nrf2 function may be potentially fatal in smoking-related lung tumorigenesis: as concluded from recent clinical investigations, lung tumor tissues harbor increased mutation or, alternatively, aberrant expression rates in either the KEAP1 or the NRF2 gene, generally resulting in constitutive Nrf2 activation, suggesting that "abuse" of Nrf2 function is an advantageous strategy of the (developing) tumor to protect itself against oxidative stress in general. On the basis of the fundamental significance of the Nrf2 pathway in smoking-dependent disease development, several attempts have been described for dietary and pharmacological intervention, the majority of which are intended to activate Nrf2 aiming at emphysema prevention. The intention of this review is to compile and discuss the various aspects of CS-Nrf2/Keap1 interaction in terms of mechanism, disease development, and chemoprevention.

Hepatoprotective effects of S-adenosylmethionine and silybin on canine hepatocytes in vitro

Inflammation and oxidative stress are associated with liver injury and development of liver disease. The transcription factors nuclear factor-kappa beta (NF-κB) and nuclear factor erythroid 2-related factor 2 (Nrf2) play critical roles in modulating liver injury and damage. Activation of NF-κB induces production of pro-inflammatory molecules including prostaglandin E2 (PGE2 ), interleukin-8 (IL-8) and macrophage chemotactic protein-1 (MCP-1). Nrf2 regulates genes controlling antioxidants. Our laboratory previously showed that hepatocytes, the primary functional cell type comprising liver tissue, respond to the cytokine interleukin-1 beta (IL-1β) by increased production of PGE2 , IL-8 and MCP-1. This increase is associated with nuclear translocation of NF-κB. In this study, we evaluated whether primary canine hepatocytes pre-treated with the combination of S-adenosylmethionine (SAMe; 30 and 2000 ng/ml) and silybin (SB; 298 ng/ml), agents with known anti-inflammatory and antioxidant properties, could attenuate IL-1β-induced inflammation and oxidative stress. The SAMe and SB combination reduced cytokine-induced PGE2 , IL-8 and MCP-1 production while also inhibiting NF-κB nuclear translocation. These changes were accompanied by increased antioxidant enzyme-reduced glutathione (GSH) comparable to control levels. The study shows for the first time that the SAMe and SB combination inhibits both inflammation and oxidative stress through two separate signalling pathways.

Evidence for cytochrome P450 2B1/2B2 isoenzymes in freshly prepared peripheral blood lymphocytes

Cytochrome P450 2B1 and 2B2, the major hepatic drug metabolizing enzymes belonging to CYP2 family and associated constitutive androstane receptor (CAR) were found to be expressed in peripheral blood lymphocytes (PBL) isolated from rats. As observed in liver, pretreatment of phenobarbital (PB) or phenytoin were found to increase the expression of CYP2B1, CYP2B2 and associated enzyme activity in PBL. Like in liver, blood lymphocyte CYP2B1/2B2 catalyzed the activity of 7-pentoxyresorufin O-dealkylase (PROD). The present data, demonstrating similarities in the regulation of blood lymphocyte CYP2B-isoenzymes with the liver enzymes, suggests that blood lymphocyte CYP2B-isoenzymes could be used as a biomarker to monitor tissue levels.

Warfarin and acetaminophen interaction: a summary of the evidence and biologic plausibility

Ms TS is a 66-year-old woman who receives warfarin for prevention of systemic embolization in the setting of hypertension, diabetes, and atrial fibrillation. She had a transient ischemic attack about 4 years ago when she was receiving aspirin. Her INR control was excellent; however, over the past few months it has become erratic, and her average dose required to maintain an INR of 2.0 to 3.0 appears to have decreased. She has had back pain over this same period and has been taking acetaminophen at doses at large as 650 mg four times daily, with her dose varying based on her symptoms. You recall a potential interaction and wonder if (1) her acetaminophen use is contributing to her loss of INR control, and (2) does this interaction place her at increased risk of warfarin-related complications?

Role of cAMP-responsive element-binding protein (CREB)-regulated transcription coactivator 3 (CRTC3) in the initiation of mitochondrial biogenesis and stress response in liver cells

Peroxisome proliferator-activated receptor α, coactivator 1α (PGC-1α) is the master regulator of mitochondrial biogenesis. PGC-1α expression is under the control of the transcription factor, cAMP-responsive element-binding protein (CREB). In searching for candidate transcription factors that mediate mitochondrial stress-initiated mitochondria-to-nucleus signaling in the regulation of mitochondrial biogenesis, we assessed the effect of silencing CREB-regulated transcription co-activators (CRTC). CRTC isoforms are co-activators of CREB-regulated transcription by a CREB phosphorylation-independent pathway. Using cultured HepG2 cells and primary mouse hepatocytes, we determined that mitochondrial stress imposed by the complex I inhibitor rotenone elicited mitochondrial biogenesis, which was dependent on an induction of PGC-1α, which was inhibited by silencing PGC-1α. PGC-1α induction in response to rotenone was inhibited by silencing the expression of CRTC3, which blocked downstream mitochondria biogenesis. In contrast, silencing CRTC2 did not affect the induction of this pathway in response to rotenone. Thus, CRTC3 plays a selective role in mitochondrial biogenesis in response to rotenone.

Elevated glutathione level does not protect against chronic alcohol mediated apoptosis in recombinant human hepatoma cell line VL-17A over-expressing alcohol metabolizing enzymes--alcohol dehydrogenase and Cytochrome P450 2E1

Chronic consumption of alcohol leads to liver injury. Ethanol-inducible Cytochrome P450 2E1 (CYP2E1) plays a critical role in alcohol mediated oxidative stress due to its ability to metabolize ethanol. In the present study, using the recombinant human hepatoma cell line VL-17A that over-expresses the alcohol metabolizing enzymes-alcohol dehydrogenase (ADH) and CYP2E1; and control HepG2 cells, the mechanism and mode of cell death due to chronic ethanol exposure were studied. Untreated VL-17A cells exhibited apoptosis and oxidative stress when compared with untreated HepG2 cells. Chronic alcohol exposure, i.e., 100 mM ethanol treatment for 72 h caused a significant decrease in viability (47%) in VL-17A cells but not in HepG2 cells. Chronic ethanol mediated cell death in VL-17A cells was predominantly apoptotic, with increased oxidative stress as the underlying mechanism. Chronic ethanol exposure of VL-17A cells resulted in 1.1- to 2.5-fold increased levels of ADH and CYP2E1. Interestingly, the level of the antioxidant GSH was found to be 3-fold upregulated in VL-17A cells treated with ethanol, which may be a metabolic adaptation to the persistent and overwhelming oxidative stress. In conclusion, the increased GSH level may not be sufficient enough to protect VL-17A cells from chronic alcohol mediated oxidative stress and resultant apoptosis.

The innate immune response to coxsackievirus B3 predicts progression to cardiovascular disease and heart failure in male mice

Background

Men are at an increased risk of dying from heart failure caused by inflammatory heart diseases such as atherosclerosis, myocarditis and dilated cardiomyopathy (DCM). We previously showed that macrophages in the spleen are phenotypically distinct in male compared to female mice at 12 h after infection. This innate immune profile mirrors and predicts the cardiac immune response during acute myocarditis.

Methods

In order to study sex differences in the innate immune response, five male and female BALB/c mice were infected intraperitoneally with coxsackievirus B3 (CVB3) or phosphate buffered saline and their spleens were harvested 12 h later for microarray analysis. Gene expression was determined using an Affymetrix Mouse Gene 1.0 ST Array. Significant gene changes were verified by quantitative real-time polymerase chain reaction or ELISA.

Results

During the innate immune response to CVB3 infection, infected males had higher splenic expression of genes which are important in regulating the influx of cholesterol into macrophages, such as phospholipase A₂ (PLA₂) and the macrophage scavenger receptor compared to the infected females. We also observed a higher expression in infected males compared to infected females of squalene synthase, an enzyme used to generate cholesterol within cells, and Cyp2e1, an enzyme important in metabolizing cholesterol and steroids. Infected males also had decreased levels of the translocator protein 18 kDa (TSPO), which binds PLA₂ and is the rate-limiting step for steroidogenesis, as well as decreased expression of the androgen receptor (AR), which indicates receptor activation. Gene differences were not due to increased viral replication, which was unaltered between sexes.

Conclusions

We found that, compared to females, male mice had a greater splenic expression of genes which are important for cholesterol metabolism and activation of the AR at 12 h after infection. Activation of the AR has been linked to increased cardiac hypertrophy, atherosclerosis, myocarditis/DCM and heart failure in male mice and humans.

Cross-study and cross-omics comparisons of three nephrotoxic compounds reveal mechanistic insights and new candidate biomarkers

The European InnoMed-PredTox project was a collaborative effort between 15 pharmaceutical companies, 2 small and mid-sized enterprises, and 3 universities with the goal of delivering deeper insights into the molecular mechanisms of kidney and liver toxicity and to identify mechanism-linked diagnostic or prognostic safety biomarker candidates by combining conventional toxicological parameters with "omics" data. Mechanistic toxicity studies with 16 different compounds, 2 dose levels, and 3 time points were performed in male Crl: WI(Han) rats. Three of the 16 investigated compounds, BI-3 (FP007SE), Gentamicin (FP009SF), and IMM125 (FP013NO), induced kidney proximal tubule damage (PTD). In addition to histopathology and clinical chemistry, transcriptomics microarray and proteomics 2D-DIGE analysis were performed. Data from the three PTD studies were combined for a cross-study and cross-omics meta-analysis of the target organ. The mechanistic interpretation of kidney PTD-associated deregulated transcripts revealed, in addition to previously described kidney damage transcript biomarkers such as KIM-1, CLU and TIMP-1, a number of additional deregulated pathways congruent with histopathology observations on a single animal basis, including a specific effect on the complement system. The identification of new, more specific biomarker candidates for PTD was most successful when transcriptomics data were used. Combining transcriptomics data with proteomics data added extra value.

Proteasome inhibitor up regulates liver antioxidative enzymes in rat model of alcoholic liver disease

Oxidative stress occurs in the liver of rats fed with alcohol chronically due to ethanol metabolism by CYP2E1, causing liver injury. The proteasome is considered as an antioxidant defense in the cell because of its activity in removing damaged and oxidized proteins, but a growing body of evidence shows that proteasome inhibitor treatment, at a non toxic low dose, provides protection against oxidative stress. In the present study, rats were fed with ethanol for 4 weeks and were treated with the proteasome inhibitor PS-341 (Bortezomib, Velcade®). Exposure to proteasome inhibitor elicited the elevation of antioxidative defense by enhancing the levels of mRNA and protein expression transcripts of glutathione reductase (GSR), glutathione synthetase (GSS), glutathione peroxidase 2 (GPX2), and superoxide dismutase 2 (SOD2) in the liver of rats fed with ethanol chronically, while ethanol alone did not increase these genes' mRNA. Our results also showed that glutamate cysteine ligase catalytic subunit (GCLC), a rate-limiting enzyme in glutathione biosynthesis, was also up regulated in the liver of rats fed with ethanol and injected with PS-431. Nrf2 mRNA level was significantly decreased in the liver of ethanol fed rats, as well as in the livers of animal fed with ethanol and treated with proteasome inhibitor, indicating that the mechanism by which proteasome inhibitor up regulates the antioxidant response element is not due to regulation of Nrf2. However, ATF4, a major regulator of antioxidant response elements, was significantly up regulated by proteasome inhibitor treatment. The beneficial effects of proteasome inhibitor treatment also reside in the reversibility of the drug because the proteasome activity was significantly increased 72 h post treatment. In conclusion, proteasome inhibitor treatment used at a non toxic low dose has potential protective effects against oxidative stress due to chronic ethanol feeding.

Nrf2-Keap1 antioxidant system and hepatic diseases

NF-E2-related factor 2 (Nrf2) is an important transcription factor. When oxidative stress occurs, Nrf2 dissociates from Keap1 (Kelch-like ECH-associating protein 1), translocates to the nucleus, and regulates the expression of genes encoding phase II detoxifying enzymes and antioxidant proteins, thereby increasing the resistance to oxidative stress and electrophilic agents. Reactive oxygen species and oxidative stress play an important role in the development of hepatic diseases. In this article, we will summarize the relationship between the Nrf2-Keap1 system and hepatic diseases.