Depletion of S-adenosyl-l-methionine with cycloleucine potentiates cytochrome P450 2E1 toxicity in primary rat hepatocytes

Discovery and Characterization of Pyridoxal 5'-Phosphate-Dependent Cycloleucine Synthases

Pyridoxal 5'-phosphate (PLP)-dependent enzymes are the most versatile biocatalysts for synthesizing nonproteinogenic amino acids. α,α-Disubstituted quaternary amino acids, such as 1-aminocyclopentane-1-carboxylic acid (cycloleucine), are useful building blocks for pharmaceuticals. In this study, starting with the biosynthesis of fusarilin A, we discovered a family of PLP-dependent enzymes that can facilitate tandem carbon-carbon forming steps to catalyze an overall [3 + 2]-annulation. In the first step, the cycloleucine synthases use SAM as the latent electrophile and an in situ-generated enamine as the nucleophile for γ-substitution. Whereas previously characterized γ-replacement enzymes protonate the resulting α-carbon and release the acyclic amino acid, cycloleucine synthases can catalyze an additional, intramolecular aldol or Mannich reaction with the nucleophilic α-carbon to form the substituted cyclopentane. Overall, the net [3 + 2]-annulation reaction can lead to 2-hydroxy or 2-aminocycloleucine products. These studies further expand the biocatalytic scope of PLP-dependent enzymes.

Treatment with S-adenosylmethionine ameliorates irinotecan-induced intestinal barrier dysfunction and intestinal microbial disorder in mice

This study aimed to investigate the protective effects of S-adenosylmethionine (SAM) on irinotecan-induced intestinal barrier dysfunction and microbial ecological dysregulation in both mice and human colon cell line Caco-2, which is widely used for studying intestinal epithelial barrier function. Specifically, this study utilized Caco-2 monolayers incubated with 7-ethyl-10-hydroxycamptothecin (SN-38) as well as an irinotecan-induced diarrhea model in mice. Our study found that SAM pretreatment significantly reduced body weight loss and diarrhea induced by irinotecan in mice. Furthermore, SAM inhibited the increase of intestinal permeability in irinotecan-treated mice and ameliorated the decrease of Zonula occludens-1(ZO-1), Occludin, and Claudin-1 expression. Additionally, irinotecan treatment increased the relative abundance of Proteobacteria compared to the control group, an effect that was reversed by SAM administration. In Caco-2 monolayers, SAM reduced the expression of reactive oxygen species (ROS) and ameliorated the decrease in transepithelial electrical resistance (TER) and increase in fluorescein isothiocyanate-dextran 4000 Da (FD-4) flux caused by SN-38. Moreover, SAM attenuated changes in the localization and distribution of ZO-1and Occludin in Caco-2 monolayers induced by SN-38 and protected barrier function by inhibiting activation of the p38 MAPK/p65 NF-κB/MLCK/MLC signaling pathway. These findings provide preliminary evidence for the potential use of SAM in treating diarrhea caused by irinotecan.

Analysis of metabolite differences between South Korean and Chinese yellow goosefish (Lophius litulon) using capillary electrophoresis time-of-flight mass spectrometry

The yellow goosefish is a benthic fish that belongs to the family Lophiidae and order Lophiiformes and is distributed in the Yellow and East China Seas. This study aimed to distinguish between yellow goosefish from different geographical origins by analyzing their metabolites. Capillary electrophoresis time-of-flight mass spectrometry was used to analyze metabolite profiles in the muscle tissues of yellow goosefish to distinguish between Korean and Chinese yellow goosefish. In total, 271 putative metabolites were extracted using 50% acetonitrile in water. Principal component analysis and orthogonal partial least squares discriminant analysis (OPLS-DA) were used to distinguish different geographical origins using the metabolite profiles obtained. The R2 and Q2 values of the OPLS-DA model were 0.856 and 0.695, respectively, indicating that the model was well-fitted and had good predictability. The heat map revealed that nucleic acid and amino compounds differed between the Korean and Chinese fish, and the variable importance in the projection scores obtained from OPLS-DA showed that there were geographical differences in the primary metabolites (5'-methylthioadenosine, adenosine, uridine 5-diphosphate, guanosine 5-diphosphate, urea, homocarnosine, O-acetylcarnitine, cycloleucine, cycloleucine S-adenosylmethionine, S-adenosylhomocysteine, ethanolamine, myo-inositol 1-phosphate), which were identified as potential candidate biomarkers.

Cladogenetic Orthogonal Light-Up Aptamers for Simultaneous Detection of Multiple Small Molecules in Cells

Recent successes in construction of light-up RNA aptamers allowed fluorescence-based live-cell imaging of RNAs. In addition, light-up aptamers have been converted into signaling aptamers that enable fluorometric detection of small chemicals. To date, only a single target chemical has been detected at a time in cells. In this study, we selected cladogenetic orthogonal light-up aptamers that output three different colors from the RNA library having the same ligand binding core. Two of the three functioned in mammalian cells. These two aptamers, which fluoresce blue and green upon binding of cognate fluorogen, were converted into signaling aptamers. Using these signaling aptamers in combination with a previously described light-up aptamer with red fluorescence, we demonstrated simultaneous detection of multiple chemicals in living cells. The cladogenetic orthogonal light-up aptamers developed in this study and the simple strategy for rational designing of the signaling aptamers will provide innovative advances in the field of RNA-based bioimaging.

Signaling Aptamer Optimization through Selection Using RNA-Capturing Microsphere Particles

An RNA signaling aptamer is composed of two units: a sensing aptamer that binds the input target molecule and a working aptamer that binds the output target molecule to result in a detectable signal. A conformational change of the signaling aptamer that induces an allosteric interaction with the output target molecule in response to the input target molecule depends on a junction region, which connects the two aptamer units. Efficient and effective optimization of the junction region remains a technical challenge. In this study, we demonstrate a simple strategy for optimizing the junction region through functional RNA selection using RNA-capturing microsphere particles. From approximately 0.2 million sequence variants, a signaling aptamer that enabled intracellular detection of S-adenosyl methionine with a high signal-to-noise ratio, which is approximately 2-fold higher relative fluorescence increment compared to the previously reported signaling aptamer, was obtained after single round of selection. The technology demonstrated here can be used to select RNA sequences that carry out specific functions in response to particular stimuli.

Early treatment efficacy of S-adenosylmethionine in patients with intrahepatic cholestasis: A systematic review

BACKGROUND

S-adenosylmethionine (AdoMet) is a metabolically pleiotropic molecule used to treat intrahepatic cholestasis (IHC) and chronic liver diseases. While the efficacy of AdoMet has been demonstrated previously, it has not been systematically investigated within the early weeks of treatment.

AIM

To systematically review the early treatment efficacy of AdoMet in adult patients with IHC.

METHODS

Studies reporting the efficacy of intravenous, intramuscular, or oral forms of AdoMet within 8 wk of treatment initiation were considered; three randomized and six non-randomized studies were eligible for inclusion (PROSPERO registration number CRD42018090936). Of the three randomized studies, two were double-blind and placebo-controlled, and one was comparator-controlled with unclear blinding and a relatively high risk of bias. Mean serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and gamma-glutamyl transferase (γGT) following AdoMet treatment vs placebo, comparator, or baseline were summarized to determine differences in liver enzymes. Changes in patient-reported clinical symptoms of cholestasis were also summarized.

RESULTS

Both placebo-controlled randomized studies reported significant reductions in serum ALT levels with AdoMet vs placebo within 2 wk. One of these also reported significant ALP reductions, and the other reported significant AST and γGT reductions within 2 wk. The comparator-controlled randomized study, which had a number of notable limitations, reported significant reductions in serum ALT and AST levels with AdoMet vs potassium magnesium aspartate within 4 wk, but not within2 wk. All of the non-randomized studies (4/4) that investigated ALT, AST, ALP and/or γGT reported significant reductions in at least two of these parameters within 2 wk. Of the five studies that evaluated fatigue, reductions were observed within 2 wk in one randomized and two non-randomized studies. The remaining two non-randomized studies reported improvements in fatigue within 6 and 8 wk. Of the four studies reporting symptoms of depression, two non-randomized studies observed improvements within 2 wk and the other two observed improvements within 17 d and 8 wk.

CONCLUSION

Data from both randomized and non-randomized studies suggest that AdoMet improves some biochemical liver parameters and symptoms of cholestasis within 2 wk, with further improvements observed in some studies after 4 and 8 wk of treatment.

Resistance of Leishmania infantum to allopurinol is associated with chromosome and gene copy number variations including decrease in the S-adenosylmethionine synthetase (METK) gene copy number

Leishmania infantum is one of the causative agents of visceral leishmaniasis (VL), a widespread, life-threatening disease. This parasite is responsible for the majority of human VL cases in Brazil, the Middle East, China, Central Asia and the Mediterranean basin. Its main reservoir are domestic dogs which, similar to human patients, may develop severe visceral disease and die if not treated. The drug allopurinol is used for the long-term maintenance of dogs with canine leishmaniasis. Following our report of allopurinol resistance in treated relapsed dogs, we investigated the mechanisms and markers of resistance to this drug. Whole genome sequencing (WGS) of clinical resistant and susceptible strains, and laboratory induced resistant parasites, was carried out in order to detect genetic changes associated with resistance. Significant gene copy number variation (CNV) was found between resistant and susceptible isolates at several loci, including a locus on chromosome 30 containing the genes LinJ.30.3550 through LinJ.30.3580. A reduction in copy number for LinJ.30.3560, encoding the S-adenosylmethionine synthetase (METK) gene, was found in two resistant clinical isolates and four induced resistant clonal strains. Using quantitative real time PCR, this reduction in METK copy number was also found in three additional resistant clinical isolates. Furthermore, inhibition of S-adenosylmethionine synthetase encoded by the METK gene in allopurinol susceptible strains resulted in increased allopurinol resistance, confirming its role in resistance to allopurinol. In conclusion, this study identified genetic changes associated with L. infantum resistance to allopurinol and the reduction in METK copy number identified may serve as a marker for resistance in dogs, and reduced protein activity correlated with increased allopurinol resistance.

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Allopurinol resistance was previously described in L. infantum isolated from dogs.

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This study aimed at defining the genetic differences between susceptible and resistant strains.

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Gene and chromosome copy numbers differed between susceptible and resistant L. infantum strains.

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Decrease in METK gene copies was associated with increased allopurinol resistance.

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Inhibition of the enzyme encoded by METK increased allopurinol resistance.

S-Adenosylmethionine Synthesis Is Regulated by Selective N6-Adenosine Methylation and mRNA Degradation Involving METTL16 and YTHDC1

S-adenosylmethionine (SAM) is an important metabolite as a methyl-group donor in DNA and histone methylation, tuning regulation of gene expression. Appropriate intracellular SAM levels must be maintained, because methyltransferase reaction rates can be limited by SAM availability. In response to SAM depletion, MAT2A, which encodes a ubiquitous mammalian methionine adenosyltransferase isozyme, was upregulated through mRNA stabilization. SAM-depletion reduced N⁶-methyladenosine (m⁶A) in the 3' UTR of MAT2A. In vitro reactions using recombinant METTL16 revealed multiple, conserved methylation targets in the 3' UTR. Knockdown of METTL16 and the m⁶A reader YTHDC1 abolished SAM-responsive regulation of MAT2A. Mutations of the target adenine sites of METTL16 within the 3' UTR revealed that these m⁶As were redundantly required for regulation. MAT2A mRNA methylation by METTL16 is read by YTHDC1, and we suggest that this allows cells to monitor and maintain intracellular SAM levels.

S-adenosylmethionine in liver health, injury, and cancer

S-adenosylmethionine (AdoMet, also known as SAM and SAMe) is the principal biological methyl donor synthesized in all mammalian cells but most abundantly in the liver. Biosynthesis of AdoMet requires the enzyme methionine adenosyltransferase (MAT). In mammals, two genes, MAT1A that is largely expressed by normal liver and MAT2A that is expressed by all extrahepatic tissues, encode MAT. Patients with chronic liver disease have reduced MAT activity and AdoMet levels. Mice lacking Mat1a have reduced hepatic AdoMet levels and develop oxidative stress, steatohepatitis, and hepatocellular carcinoma (HCC). In these mice, several signaling pathways are abnormal that can contribute to HCC formation. However, injury and HCC also occur if hepatic AdoMet level is excessive chronically. This can result from inactive mutation of the enzyme glycine N-methyltransferase (GNMT). Children with GNMT mutation have elevated liver transaminases, and Gnmt knockout mice develop liver injury, fibrosis, and HCC. Thus a normal hepatic AdoMet level is necessary to maintain liver health and prevent injury and HCC. AdoMet is effective in cholestasis of pregnancy, and its role in other human liver diseases remains to be better defined. In experimental models, it is effective as a chemopreventive agent in HCC and perhaps other forms of cancer as well.

Aberrant hepatic methionine metabolism and gene methylation in the pathogenesis and treatment of alcoholic steatohepatitis

The pathogenesis of alcoholic steatohepatitis (ASH) involves ethanol-induced aberrations in hepatic methionine metabolism that decrease levels of S-adenosylmethionine (SAM), a compound which regulates the synthesis of the antioxidant glutathione and is the principal methyl donor in the epigenetic regulation of genes relevant to liver injury. The present paper describes the effects of ethanol on the hepatic methionine cycle, followed by evidence for the central role of reduced SAM in the pathogenesis of ASH according to clinical data and experiments in ethanol-fed animals and in cell models. The efficacy of supplemental SAM in the prevention of ASH in animal models and in the clinical treatment of ASH will be discussed.

Vitamin-dependent methionine metabolism and alcoholic liver disease

Emerging evidence indicates that ethanol-induced alterations in hepatic methionine metabolism play a central role in the pathogenesis of alcoholic liver disease (ALD). Because malnutrition is a universal clinical finding in this disease and hepatic methionine metabolism is dependent upon dietary folate and vitamins B-6 and B-12, ALD can be considered an induced nutritional disorder that is conditioned by alcohol abuse. The present review describes the etiologies of these 3 vitamin deficiencies in ALD and how they interact with chronic ethanol exposure to alter hepatic methionine metabolism. Subsequent sections focus on molecular mechanisms for the interactions of aberrant methionine metabolism with ethanol in the pathogenesis of ALD, in particular the role of S-adenosylmethionine (SAM) in regulating the epigenetic expressions of genes relevant to pathways of liver injury. The review will conclude with descriptions of studies on the efficacy of SAM in the treatment of ALD and with discussion of potentially fruitful future avenues of research.

Bimodal targeting of microsomal cytochrome P450s to mitochondria: implications in drug metabolism and toxicity

IMPORTANCE OF THE FIELD

Microsomal CYPs are critical for drug metabolism and toxicity. Recent studies show that these CYPs are also present in the mitochondrial compartment of human and rodent tissues. Mitochondrial CYP1A1 and 2E1 show both overlapping and distinct metabolic activities compared to microsomal forms. Mitochondrial CYP2E1 also induces oxidative stress. The mechanisms of mitochondria targeting of CYPs and their role in drug metabolism and toxicity are important factors to consider while determining the drug dose and in drug development.

AREAS COVERED IN THIS REVIEW

This review highlights the mechanisms of bimodal targeting of CYP1A1, 2B1, 2E1 and 2D6 to mitochondria and microsomes. The review also discusses differences in structure and function of mitochondrial CYPs.

WHAT THE READERS WILL GAIN

A comprehensive review of the literature on drug metabolism in the mitochondrial compartment and their potential for inducing mitochondrial dysfunction.

TAKE HOME MESSAGE

Studies on the biochemistry, pharmacology and pharmacogenetic analysis of CYPs are mostly focused on the molecular forms associated with the microsomal membrane. However, the mitochondrial CYPs in some individuals can represent a substantial part of the tissue pool and contribute in a significant way to drug metabolism, clearance and toxicity.

Hepatoprotective effects of S-adenosyl-L-methionine against alcohol- and cytochrome P450 2E1-induced liver injury

S-adenosyl-L-methionine (SAM) acts as a methyl donor for methylation reactions and participates in the synthesis of glutathione. SAM is also a key metabolite that regulates hepatocyte growth, differentiation and death. Hepatic SAM levels are decreased in animal models of alcohol liver injury and in patients with alcohol liver disease or viral cirrhosis. This review describes the protection by SAM against alcohol and cytochrome P450 2E1-dependent cytotoxicity both in vitro and in vivo and evaluates mechanisms for this protection.

Changes in the expression of methionine adenosyltransferase genes and S-adenosylmethionine homeostasis during hepatic stellate cell activation

Hepatic stellate cell (HSC) activation is an essential event during liver fibrogenesis. Methionine adenosyltransferase (MAT) catalyzes biosynthesis of S-adenosylmethionine (SAMe), the principle methyl donor. SAMe metabolism generates two methylation inhibitors, methylthioadenosine (MTA) and S-adenosylhomocysteine (SAH). Liver cell proliferation is associated with induction of two nonliver-specific MATs: MAT2A, which encodes the catalytic subunit alpha2, and MAT2beta, which encodes a regulatory subunit beta that modulates the activity of the MAT2A-encoded isoenzyme MATII. We reported that MAT2A and MAT2beta genes are required for liver cancer cell growth that is induced by the profibrogenic factor leptin. Also, MAT2beta regulates leptin signaling. The strong association of MAT genes with proliferation and leptin signaling in liver cells led us to examine the role of these genes during HSC activation. MAT2A and MAT2beta are induced in culture-activated primary rat HSCs and HSCs from 10-day bile duct ligated (BDL) rat livers. HSC activation led to a decline in intracellular SAMe and MTA levels, a drop in the SAMe/SAH ratio, and global DNA hypomethylation. The decrease in SAMe levels was associated with lower MATII activity during activation. MAT2A silencing in primary HSCs and MAT2A or MAT2beta silencing in the human stellate cell line LX-2 resulted in decreased collagen and alpha-smooth muscle actin (alpha-SMA) expression and cell growth and increased apoptosis. MAT2A knockdown decreased intracellular SAMe levels in LX-2 cells. Activation of extracellular signal-regulated kinase and phosphatidylinositol-3-kinase signaling in LX-2 cells required the expression of MAT2beta but not that of MAT2A.

CONCLUSION

MAT2A and MAT2beta genes are induced during HSC activation and are essential for this process. The SAMe level falls, resulting in global DNA hypomethylation.

Inhibition of the mitochondrial permeability transition by cyclosporin A prevents pyrazole plus lipopolysaccharide-induced liver injury in mice

Previous results showed that pyrazole potentiates lipopolysaccharide (LPS)-induced liver injury in mice. Mechanisms involved the overexpression of cytochrome P450 2E1 (CYP2E1), oxidative stress, and activation of c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK). The current study was carried out to test the hypothesis that the mitochondria permeability transition (MPT) plays a role in this pyrazole plus LPS toxicity. Mice were injected intraperitoneally with pyrazole for 2 days, followed by a challenge with LPS with or without treatment with cyclosporin A (CsA), an inhibitor of the MPT. Serum alanine aminotransferase and aspartate aminotransferase were increased by pyrazole plus LPS treatment, and CsA treatment could attenuate these increases. CsA also prevented pyrazole plus LPS-induced hepatocyte necrosis. Formation of 4-hydroxynonenal protein adducts and 3-nitrotyrosine protein adducts in liver tissue was increased by the pyrazole plus LPS treatment, and CsA treatment blunted these increases. Swelling, cytochrome c release from mitochondria to the cytosol, and lipid peroxidation were increased in mitochondria isolated from the pyrazole plus LPS-treated mice, and CsA treatment prevented these changes. CsA did not prevent the increased levels of inducible nitric oxide synthase (iNOS), tumor necrosis factor-alpha (TNF-alpha), pp38 MAPK, and p-JNK2. In conclusion, although CsA does not prevent elevations in upstream mediators of the pyrazole plus LPS toxicity (iNOS, TNF-alpha, CYP2E1, MAPK), it does protect mice from the pyrazole plus LPS-induced liver toxicity by preventing the MPT and release of cytochrome c and decreasing mitochondrial oxidative stress. These results indicate that mitochondria are the critical targets of pyrazole plus LPS in mediating liver injury.

The double danger of ethanol and hypoxia: their effects on a hepatoma cell line

Alcohol use has become far too prevalent in our society. Alcohol kills 6.5 times more youth than all other illicit drugs combined. In combination with traumatic and hemorrhagic injuries, alcohol results in a much higher mortality rate. Alcohol, alone and in high dosages, also causes great damage to the body, often leading to death as well. Thus, it is of utmost importance that research is conducted to help explain the pathological mechanism of high fatalities and injuries associated with alcohol use. In order to simulate this complex situation in vitro, a rat hepatoma cell line (H-II-4-E) was exposed to various concentrations of ethanol as well as the condition of hypoxia. Hypoxia mimics the primary level of tissue damage caused by hemorrhage after impact in a car accident. In this way, we tested the hypothesis that the presence of ethanol in combination with hypoxia causes greater cellular damage compared to conditions of ethanol or hypoxia alone. Ethanol, alone and in high concentrations, was found to greatly affect cell function as shown by decreased cellular ATP levels, increased LDH release, and a downregulated expression of CYP2E1 gene. By adding the condition of hypoxia to low concentrations of ethanol, cellular damage increased dramatically as well. Decreased gene expression and protein levels of CYP2E1 correlated with increased hepatocyte injury and thus, this enzyme may significantly contribute to the severity of cellular damage. These results provide useful information for future research on the effects of ethanol in combination with hemorrhage on cells in vitro, simulating the condition of driving while intoxicated and binge drinking.

Negundoside, an iridiod glycoside from leaves of Vitex negundo, protects human liver cells against calcium-mediated toxicity induced by carbon tetrachloride

AIM: To evaluate the protective effect of 2'-p-hydroxybenzoylmussaenosidic acid [negundoside (NG), against carbon tetrachloride (CCl₄)-induced toxicity in HuH-7 cells.

METHODS: CCl₄ is a well characterized hepatotoxin, and inducer of cytochrome P450 2E1 (CYP2E1)-mediated oxidative stress. In addition, lipid peroxidation and accumulation of intracellular calcium are important steps in the pathway involved in CCl₄ toxicity. Liver cells (HuH-7) were treated with CCl₄, and the mechanism of the cytoprotective effect of NG was assessed. Silymarin, a known hepatoprotective drug, was used as control.

RESULTS: NG protected HuH-7 cells against CCl₄ toxicity and loss of viability without modulating CYP2E1 activity. Prevention of CCl₄ toxicity was associated with a reduction in oxidative damage as reflected by decreased generation of reactive oxygen species (ROS), a decrease in lipid peroxidation and accumulation of intracellular Ca²⁺ levels and maintenance of intracellular glutathione homeostasis. Decreased mitochondrial membrane potential (MMP), induction of caspases mediated DNA fragmentation and cell cycle arrest, as a result of CCl₄ treatment, were also blocked by NG. The protection afforded by NG seemed to be mediated by activation of cyclic adenosine monophosphate (cAMP) synthesis and inhibition of phospholipases (cPLA2).

CONCLUSION: NG exerts a protective effect on CYP2E1-dependent CCl₄ toxicity via inhibition of lipid peroxidation, followed by an improved intracellular calcium homeostasis and inhibition of Ca²⁺-dependent proteases.

A decrease in S-adenosyl-L-methionine potentiates arachidonic acid cytotoxicity in primary rat hepatocytes enriched in CYP2E1

Previous studies show that treatment with a polyunsaturated fatty acid, arachidonic acid (AA), or high concentrations of cycloleucine, an inhibitor of methionine adenosyltransferase (MAT), which lowers levels of S-adenosyl-L-methionine (SAM), increased toxicity in hepatocytes from pyrazole-treated rats which expressed high levels of cytochrome P450 2E1 (CYP2E1). In this study, I used concentrations of cycloleucine or AA, which by themselves do not produce any toxicity, to evaluate whether a decrease in SAM sensitizes hepatocytes to AA toxicity, especially in hepatocytes enriched in CYP2E1. Levels of SAM were lower by 50% in hepatocytes from pyrazole- compared to saline-treated rats. Cycloleucine treatment caused a 50% decline in SAM levels with both hepatocyte preparations and SAM levels were lowest in the pyrazole-treated hepatocytes. The combination of cycloleucine plus AA produced some toxicity and apoptosis in hepatocytes from saline-treated rats but increased toxicity and apoptosis was found in the hepatocytes from pyrazole-treated rats. Cytotoxicity could be prevented by incubation with SAM, the antioxidant trolox, and the mitochondrial permeability transition inhibitor trifluoperazine. The enhanced cytotoxicity could also be protected by treating rats with chlormethiazole, a specific inhibitor of CYP2E1, thus validating the role of CYP2E1. Cycloleucine plus AA treatment elevated production of reactive oxygen species (ROS) and lipid peroxidation to greater extents with the hepatocytes from pyrazole-treated rats than that from the saline-treated rats. I hypothesize that increased production of ROS by hepatocytes enriched in CYP2E1 potentiates AA-induced lipid peroxidation and toxicity when hepatoprotective levels of SAM are lowered. Such interactions, e.g. induction of CYP2E1, decline in SAM and polyunsaturated fatty acid-induced lipid peroxidation, may contribute to alcohol-induced liver injury.