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Trousil S, Lee P, Edwards RJ, Maslen L, Lozan-Kuehne JP, Ramaswami R, Aboagye EO, Clarke S, Liddle C, Sharma R. Altered cytochrome 2E1 and 3A P450-dependent drug metabolism in advanced ovarian cancer correlates to tumour-associated inflammation. Br J Pharmacol 2019; 176:3712-3722. [PMID: 31236938 DOI: 10.1111/bph.14776] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 05/10/2019] [Accepted: 05/16/2019] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND AND PURPOSE Previous work has focussed on changes in drug metabolism caused by altered activity of CYP3A in the presence of inflammation and, in particular, inflammation associated with malignancy. However, drug metabolism involves a number of other P450s, and therefore, we assessed the effect of cancer-related inflammation on multiple CYP enzymes using a validated drug cocktail. EXPERIMENTAL APPROACH Patients with advanced stage ovarian cancer and healthy volunteers were recruited. Participants received caffeine, chlorzoxazone, dextromethorphan, and omeprazole as in vivo probes for CYP1A2, CYP2E1, CYP2D6, CYP3A, and CYP2C19. Blood was collected for serum C-reactive protein and cytokine analysis. KEY RESULTS CYP2E1 activity was markedly up-regulated in cancer (6-hydroxychlorzoxazone/chlorzoxazone ratio of 1.30 vs. 2.75), while CYP3A phenotypic activity was repressed in cancer (omeprazole sulfone/omeprazole ratio of 0.23 vs. 0.49). Increased activity of CYP2E1 was associated with raised serum levels of IL-6, IL-8, and TNF-α. Repression of CYP3A correlated with raised levels of serum C-reactive protein, IL-6, IL-8, and TNF-α. CONCLUSIONS AND IMPLICATIONS CYP enzyme activity is differentially affected by the presence of tumour-associated inflammation, affecting particularly CYP2E1- and CYP3A-mediated drug metabolism, and may have profound implications for drug development and prescribing in oncological settings.
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Affiliation(s)
- Sebastian Trousil
- Department of Surgery and Cancer, Imperial College London, London, UK
| | - Patrizia Lee
- Department of Surgery and Cancer, Imperial College London, London, UK
| | - Robert J Edwards
- Division of Experimental Medicine, Imperial College London, London, UK
| | - Lynn Maslen
- Department of Surgery and Cancer, Imperial College London, London, UK
| | | | - Ramya Ramaswami
- Department of Surgery and Cancer, Imperial College London, London, UK
| | - Eric O Aboagye
- Department of Surgery and Cancer, Imperial College London, London, UK
| | - Stephen Clarke
- Department of Medical Oncology, Royal North Shore Hospital, St Leonards, NSW, Australia
| | - Christopher Liddle
- Storr Liver Unit, Westmead Millennium Institute, University of Sydney, Westmead, Westmead, NSW, Australia
| | - Rohini Sharma
- Department of Surgery and Cancer, Imperial College London, London, UK
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Rani V, Verma Y, Rana K, Rana SVS. Zinc oxide nanoparticles inhibit dimethylnitrosamine induced liver injury in rat. Chem Biol Interact 2017; 295:84-92. [PMID: 29024620 DOI: 10.1016/j.cbi.2017.10.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 10/06/2017] [Indexed: 02/07/2023]
Abstract
Dimethylnitrosamine (DMN) is a potent hepatotoxic, carcinogenic and mutagenic compound. It induces massive liver cell necrosis and death in experimental animals. Several drugs have been tested in the past for their protective behavior against DMN toxicity. However, it is for the first time that therapeutic intervention of ZnONPs (zinc oxide nanoparticles) has been studied against its toxicity. Present results show that a post treatment of ZnONPs (50 mg/kg) to DMN (2 μl/100 g body weight) treated rats reduces lipid peroxidation, oxidative stress and fibrosis in the liver. It diminishes serum ALT (alanine transaminases), AST (aspartate transaminases) and LDH (lactate dehydrogenase) showing improvement in liver function. Reduced values of proinflammatory cytokines viz. TNF-α and IL-12 also support its protective effects. Histopathological observations also indicate improvement in liver cell morphology. It is postulated that ZnONPs offer protection through selective toxicity to proliferating tissue including adenomatous islands formed in the liver. Zinc metallothionein (Zn-MT) induced by ZnONPs may also contribute in the amelioration of DMN induced toxic effects. Diminution of oxidative stress by ZnONPs remains to be the key mechanism involved in its protective effects. However, toxicity of ZnONPs in the liver needs to be monitored simultaneously.
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Affiliation(s)
- Varsha Rani
- Toxicology Laboratory, Department of Zoology/Toxicology, Chaudhary Charan Singh University, Meerut 250004, India
| | - Yeshvandra Verma
- Toxicology Laboratory, Department of Zoology/Toxicology, Chaudhary Charan Singh University, Meerut 250004, India
| | - Kavita Rana
- Toxicology Laboratory, Department of Zoology/Toxicology, Chaudhary Charan Singh University, Meerut 250004, India
| | - Suresh Vir Singh Rana
- Toxicology Laboratory, Department of Zoology/Toxicology, Chaudhary Charan Singh University, Meerut 250004, India.
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Sen A, Terzioglu G, Atmaca P, Celik G, Ozgun O, Arslan S. Modulatory actions ofo-coumaric acid on carcinogen-activating cytochrome P450 isozymes and the potential for drug interactions in human hepatocarcinoma cells. PHARMACEUTICAL BIOLOGY 2015; 53:1391-8. [PMID: 25880144 DOI: 10.3109/13880209.2015.1014919] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Alaattin Sen
- Department of Biology, Pamukkale University , Kinikli Campus, Denizli , Turkey
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4
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Abstract
Over the last three decades, direct hepatotoxic effects of ethanol were established, some of which were linked to redox changes produced by NADH generated via the alcohol dehydrogenase (ADH) pathway and shown to affect the metabolism of lipids, carbohydrates, proteins, and purines. It was also determined that ethanol can be oxidized by a microsomal ethanol oxidizing system (MEOS) involving a specific cytochrome P-450; this newly discovered ethanol-inducible cytochrome P-450 (P-450 IIEi) contributes to ethanol metabolism, tolerance, energy wastage (with associated weight loss), and the selective hepatic perivenular toxicity of various xenobiotics. Their activation by P-450IIEi now provides an understanding of the increased susceptibility of the heavy drinker to the toxicity of industrial solvents, anaesthetic agents, commonly prescribed drugs, over-the-counter analgesics, and chemical carcinogens. P-450 induction also explains depletion (and toxicity) of nutritional factors such as vitamin A. As a consequence, treatment with vitamin A and other nutritional factors is beneficial, but must take into account a narrowed therapeutic window in alcoholics who have increased needs for nutrients and also display an enhanced susceptibility to some of their adverse effects. Acetaldehyde (the metabolite produced from ethanol by either ADH or MEOS) impairs hepatic oxygen utilization and forms protein adducts, resulting in antibody production, enzyme inactivation, and decreased DNA repair. It also stimulates collagen production by the vitamin A storing cells (lipocytes) and myofibroblasts, and causes glutathione depletion. Supplementation with S-adenosyl-L-methionine partly corrects the depletion and associated mitochondrial injury, whereas administration of polyunsaturated lecithin opposes the fibrosis. Thus, at the cellular level, the classic dichotomy between the nutritional and toxic effects of ethanol has now been bridged. The understanding of how the ensuing injury eventually results in irreversible scarring or cirrhosis may provide us with improved modalities for treatment and prevention.
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Affiliation(s)
- C S Lieber
- Alcohol Research & Treatment Center, Bronx VA Medical Center, 130 West Kingsbridge Road, Bronx, NY, 10468, USA
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5
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Arslan S, Ozgun O. Cyclamen Trochopteranthum: Cytotoxic activity and possible adverse interactions including drugs and carcinogens. Chin J Integr Med 2012. [PMID: 23001494 DOI: 10.1007/s11655-012-1253-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Indexed: 12/08/2022]
Abstract
OBJECTIVE: To examine the effect of water extracts of cyclamen tubers on the expression of main cytochrome P450 (CYP450s) including CYP1A1, CYP1A2 CYP2E1, CYP2B6, CYP2C9 and CYP3A4 that participate in the metabolism of both drugs and carcinogens and cytotoxic activity in human cancer cell lines, namely HepG2 and Caco-2. METHODS: Cyclamen trochopteranthum tubers were extracted with dH(2)O and then lyophilized under vacuum. Infrared spectral study was made for extracts by Fourier transform infrared spectroscopy (FT-IR). Cytotoxic activity of cyclamen was determined by crystal violet staining in HepG2 and Caco-2 cells. CYP expression was determined by reverse transcription polymerase chain reaction (RT-PCR). RESULTS: Cyclamen water extract had moderate cytotoxic activity. It was found that lethal concentration (LC50) value of the cyclamen extract was 50 and 125 μg/mL in HepG2 and Caco-2 cell lines, respectively. Moreover, it caused induction and suppression of CYP450s mRNA levels in HepG2 and Caco-2 cells. CONCLUSION: Cyclamen may have a potential not only inhibition and/or induction of the metabolism of certain co-administered drugs but also development of toxicity, mutagenesis and malignant transformation due to induction or suppression of the CYP450s dependent drug metabolizing enzymes.
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Affiliation(s)
- Sevki Arslan
- Department of Biology, Pamukkale University, Denizli, 20070, Turkey,
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6
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Diverse action of acrylamide on cytochrome P450 and glutathione S-transferase isozyme activities, mRNA levels and protein levels in human hepatocarcinoma cells. Cell Biol Toxicol 2012; 28:175-86. [PMID: 22392284 DOI: 10.1007/s10565-012-9214-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Accepted: 02/17/2012] [Indexed: 12/08/2022]
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7
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Robinson BL, Guinnup DE, Andrews JE, Allis JW, McDonald A, Seely JC, Mohin TJ, Simmons JE. Hepatic and Renal Assessment of Acute Exposure to Inhaled Epichlorohydrin: Toxicological Evaluation and Exposure Modeling. Inhal Toxicol 2008. [DOI: 10.3109/08958379509029099] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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8
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Wang T, Shankar K, Ronis MJ, Mehendale HM. Mechanisms and outcomes of drug- and toxicant-induced liver toxicity in diabetes. Crit Rev Toxicol 2007; 37:413-59. [PMID: 17612954 DOI: 10.1080/10408440701215100] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Increase dincidences of hepatotoxicity have been observed in diabetic patients receiving drug therapies. Neither the mechanisms nor the predisposing factors underlying hepatotoxicity in diabetics are clearly understood. Animal studies designed to examine the mechanisms of diabetes-modulated hepatotoxicity have traditionally focused only on bioactivation/detoxification of drugs and toxicants. It is becoming clear that once injury is initiated, additional events determine the final outcome of liver injury. Foremost among them are two leading mechanisms: first, biochemical mechanisms that lead to progression or regression of injury; and second, whether or not timely and adequate liver tissue repair occurs to mitigate injury and restore liver function. The liver has a remarkable ability to repair and restore its structure and function after physical or chemical-induced damage. The dynamic interaction between biotransformation-based liver injury and compensatory tissue repair plays a pivotal role in determining the ultimate outcome of hepatotoxicity initiated by drugs or toxicants. In this review, mechanisms underlying altered hepatotoxicity in diabetes with emphasis on both altered bioactivation and liver tissue repair are discussed. Animal models of both marked sensitivity (diabetic rats) and equally marked protection (diabetic mice) from drug-induced hepatotoxicity are described. These examples represent a remarkable species difference. Availability of the rodent diabetic models offers a unique opportunity to uncover mechanisms of clinical interest in averting human diabetic sensitivity to drug-induced hepatotoxicities. While the rat diabetic models appear to be suitable, the diabetic mouse models might not be suitable in preclinical testing for potential hepatotoxic effects of drugs or toxicants, because regardless of type 1 or type2 diabetes, mice are resistant to acute drug-or toxicant-induced toxicities.
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Affiliation(s)
- T Wang
- Department of Toxicology, College of Pharmacy, University of Louisiana at Monroe, Monroe, Louisiana 71209, USA
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9
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Morel G, Cossec B, Lambert AM, Binet S. Evaluation of rat hepatic 2E1 activity in function of age, sex and inducers: choice of an experimental model capable of testing the hepatotoxicity of low molecular weight compounds. Toxicol Lett 1999; 106:171-80. [PMID: 10403661 DOI: 10.1016/s0378-4274(99)00058-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The aim of this work on rat hepatic P450 2E1 activity was to seek the most suitable experimental model to study the role of cytochrome P450 2E1 in the metabolism of industrial chemicals. Two sets of experiments were devoted to selecting the age and sex of animals and to estimating the response of male and female rats to different inducers. In the first set, the effect of three inducers (fasting; ethanol; acetone) was studied in male rats aged 5, 7 and 9 weeks. In the second set, the effect of different inducers, namely beta-naphthoflavone (BNF), phenobarbital (PB), ethanol, acetone and pyridine, on PNP and chlorzoxazone (CLZO) hydroxylase activities was studied in 7 week old male and female rats. The results demonstrate firstly that microsomal p-nitrophenol (PNP) hydroxylase activity significantly decreases in control male rats in inverse function of age, and secondly that induction by ethanol decreases with age. The PNP hydroxylase activity level of controls and the significant increases in PNP hydroxylase activity observed in 7 week old male rats show that this is the most suitable age for the second set of experiments. In this second set, it was shown that P450 1A (induced by BNF) is involved in CLZO hydroxylase activity only. PB increased the hydroxylase activities in male and female rats by about 1.5 and 1.7 times those of the controls, respectively. The effects of P450 2E1 inducers in function of sex show that male rats exhibited more significant increases in PNP and CLZO hydroxylase activities than female. The specificity of these two substrates is discussed. Neither of these two reactions was specifically catalysed by P450 2E1, but PNP may be considered as the most specific and the least sensitive substrate. In addition, the linear relationship observed between the two substrates (PNP and CLZO) showed a good correlation between their activities (r = 0.90, P < 0.001). In conclusion, these results suggest the use of the 7 week old male rat as the experimental model to study the role of cytochrome P450 2E1 in the hepatotoxicity of low molecular weight industrial chemicals.
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Affiliation(s)
- G Morel
- Institut National de Recherche et de Sécurité, Vandoeuvre, France
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10
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Schulze J. Presystemic intestinal metabolism of N-nitrosodimethylamine in mouse intestine. CANCER DETECTION AND PREVENTION 1999; 23:107-15. [PMID: 10101591 DOI: 10.1046/j.1525-1500.1999.09913.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
N-Nitrosodimethylamine (NDMA), a common food contaminant, is a potent liver carcinogen in rodents. A high presystemic intestinal metabolism has been shown for several nitrosamines including environmentally important compounds. We determined the metabolism of 1 micron [14C]-NDMA in isolated perfused mouse intestinal segments. We found NDMA to be equally distributed between the absorbed fluid and the perfusate. During a 2-h perfusion period, 0.13% of the radioactivity was converted to CO2. The formation of CO2 was decreased by pretreatment with diallylsulfide or addition of SKF 525A, and slightly increased by phenobarbital. Hydrophilic metabolites were found in the absorbate (0.9%) and perfusate (3.8%) of untreated mice. The amount of metabolites in the absorbate was increased by treatment with acetone or phenobarbital (8-fold), but not after starvation, with formaldehyde being present only in phenobarbital-treated animals. Treatment with diallylsulfide or addition of SKF 525A reduced the amount of metabolites in acetone-treated animals to control values. In conclusion, intestinal turnover does not significantly reduce the body burden of orally ingested NDMA and thus is not a first-line defense against this carcinogenic nitrosamine. NDMA metabolism has been attributed to the presence of cytochrome P450IIE1, which has not been detected in the intestine of untreated animals. The low turnover of NDMA, the induction by acetone and phenobarbital treatment, and the inhibition by diallylsulfide suggest the presence of low amounts of this or related cytochrome P450 isozyme(s) in mouse intestine.
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Affiliation(s)
- J Schulze
- Walther-Straub Institute of Pharmacology and Toxicology, Ludwig Maximilians Universität München, Germany
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11
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Oesch-Bartlomowicz B, Padma PR, Becker R, Richter B, Hengstler JG, Freeman JE, Wolf CR, Oesch F. Differential modulation of CYP2E1 activity by cAMP-dependent protein kinase upon Ser129 replacement. Exp Cell Res 1998; 242:294-302. [PMID: 9665827 DOI: 10.1006/excr.1998.4120] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Many toxic compounds are activated by cytochrome P450 (CYP) 2E1 to reactive metabolites, which represents a potential hazard for cellular homeostasis. Therefore knowledge about CYP2E1 regulation could be of great biological importance. It has been shown that CYP2E1 is controlled transcriptionally and post-translationally by phosphorylation. In the present study we investigated the role of serine-129 (Ser129) in the protein kinase A (PKA) recognition sequence motif Arg-Arg-Phe-Ser129. To gain further insights into the possible relevance of Ser129 for CYP2E1 function, Ser129 was replaced by alanine (Ala) or glycine (Gly) by site-directed mutations of the cDNA coding for CYP2E1. The mutant cDNAs were transfected into Chinese hamster lung fibroblast V79 cells. Despite the mutation in the PKA phosphorylation motif, all strains produced catalytically active CYP2E1. However, there was a marked change in the substrate preference: The Gly129-containing strains hydroxylated p-nitrophenol (PNP) to a markedly higher extent than the wild-type cDNA-containing cells, while they demethylated N-nitrosodimethylamine (NDMA) to a markedly lower extent than the wild-type cells. All the strains activated NDMA to mutagenic products. Treatment with the membrane-permeating cAMP derivative db-cAMP reduced markedly both the PNP hydroxylase and the NDMA demethylase activities as well as the mutation frequency induced by NDMA in the Ser129-containing strain. This decrease in activity was not accompanied by a decrease in CYP2E1 content. In addition, the catalytic activities of CYP2E1 were decreased in microsomes from rat hepatocytes treated with db-cAMP. Also in this case, the decrease in activities was not accompanied by a decrease in enzyme protein. These findings argue that involvement of Ser129 and its phosphorylation is not in determining CYP2E1 protein level, but rather in controlling its catalytic activity. In contrast, in the strains containing Ala129 or Gly129, treatment with db-cAMP caused a marked increase in both PNP hydroxylase and NDMA demethylase. In these strains a similar db-cAMP-mediated increase was also observed in the mutation frequency, resulting from the treatment with the promutagen NDMA, which is activated by CYP2E1. Our results show that CYP2E1 in V79 cells responds in two separate ways to db-cAMP exposure depending on the amino acid residue present in the PKA recognition sequence. The enzyme is committed to a negative regulation by db-cAMP if Ser129 is the target amino acid for PKA, leading to a decrease in the metabolic activation to mutagenic and carcinogenic species. On the other hand, Ala129 or Gly129 substitution directed CYP2E1 toward a positive regulation by increasing its catalytic activities and metabolic activation to mutagenic intermediates in the presence of db-cAMP. We also obtained evidence that cAMP-mediated downregulation of wild-type (Ser129) CYP2E1 was not accompanied by its destruction but instead by its stabilization, which shows that Ser129 is not involved in CYP2E1 degradation but dictates requirements for its specific activities.
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12
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Clarke J, Snelling J, Ioannides C, Flatt PR, Barnett CR. Effect of vitamin C supplementation on hepatic cytochrome P450 mixed-function oxidase activity in streptozotocin-diabetic rats. Toxicol Lett 1996; 89:249-56. [PMID: 9001594 DOI: 10.1016/s0378-4274(96)03822-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The effect of vitamin C supplementation on hepatic cytochrome P450 expression was investigated in streptozotocin (STZ) diabetic male Wistar Albino rats. STZ-treated rats displayed the usual characteristics of diabetes including; hyperphagia, polydipsia, decreased body weight gain and also the increased expression and activity of hepatic CYP1A, 2B, 2E and 4A proteins. Vitamin C administration in drinking water (2% w/v) was associated with significant decreases in the levels of hyperglycaemia (P < 0.05), glycosylated haemoglobin (P < 0.05), hyperlipidaemia (P < 0.001), and hyperketonaemia (P < 0.001) associated with STZ-diabetes. Vitamin C-treatment selectively reduced the activity and expression of CYP2E proteins (P < 0.001). These effects on CYP2E expression may be mediated by the reduced levels of circulating ketone bodies, however, a direct effect on CYP2E expression in diabetes cannot be discounted.
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Affiliation(s)
- J Clarke
- School of Biomedical Sciences, University of Ulster, Londonderry, Northern Ireland, UK
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Affiliation(s)
- S Dhillon
- ICF Kaiser Engineers, Oakland, CA 94612, USA
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14
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Brown BL, Allis JW, Simmons JE, House DE. Fasting for less than 24 h induces cytochrome P450 2E1 and 2B1/2 activities in rats. Toxicol Lett 1995; 81:39-44. [PMID: 8525497 DOI: 10.1016/0378-4274(95)03407-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cytochrome P450 (CYP) 2E1 activity is induced after 24 h of fasting but no information is available for shorter fasting periods. We investigate the induction of CYP 2E1, 2B1/2 and 1A1 in young adult male F344 rats after 8, 16 and 24 h of fasting compared to control. Liver microsomes were analyzed for the following enzyme activities: p-nitrophenol hydroxylase (PNP) for CYP 2E1, pentoxyresorufin-O-dealkylase (PROD) for CYP 2B1/2 and ethoxyresorufin-O-deethylase (EROD) for CYP 1A1. After each fasting interval, the activities per mg microsomal protein for PNP and PROD increased but the activity of EROD remained unchanged. Western blots for CYP 2E1 and CYP 2B1 showed increases comparable to the PNP and PROD activities, respectively. On a whole organ basis, increases were found for PNP and PROD activities, while decreases were found for EROD activity and total microsomal protein. The results are consistent with an induction of CYP 2E1 and CYP 2B1/2 activities after as little as 8 h of fasting.
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Affiliation(s)
- B L Brown
- Health Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA
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Sohn OS, Fiala ES. Effects of dietary restriction and fasting on selected rat liver enzymes of xenobiotic metabolism and on AOM-induced DNA guanine methylation in rat liver and colon. Nutr Cancer 1995; 23:13-22. [PMID: 7739911 DOI: 10.1080/01635589509514357] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Using five- to eight-week-old male F344 rats and a high-fat (23.5% corn oil) modified AIN-76A diet, we examined the effects of dietary restriction (a 3-wk 30% reduction of food intake with respect to ad libitum-fed controls) or complete fasting (2 days without food) on the activities of hepatic xenobiotic metabolizing enzymes in vitro and on azoxymethane- (AOM) induced formation of O6-methylguanine and 7-methylguanine in liver and colon DNA in vivo. Compared with ad libitum-fed rats, fasting increased total liver cytochrome P450 by 32%, microsomal aniline hydroxylase by 270%, N-nitrosodimethylamine demethylase by 270%, and azoxymethane hydroxylase by 320%. Liver benzo[a]pyrene (BP) hydroxylase and glutathione-S-transferase were decreased by 39% and 21%, respectively, whereas NADPH cytochrome c reductase and UDP glucuronyltransferase were unchanged. DNA methylation in the livers of fasted animals was 20-31% greater six hours after a 15 mg/kg sc injection of AOM than in ad libitum-fed controls, whereas DNA methylation in the colon was slightly lower. In three-week diet-restricted animals. there were small but not statistically significant changes in the various enzyme activities and in AOM-induced DNA methylation compared with the ad libitum-fed controls, with the exception of BP hydroxylase, which showed a 26% decrease. However, the trends in the increase or decrease of each parameter, although small in magnitude, were similar to those observed in the case of fasting, suggesting that the effects might become significant if the duration of diet restriction were prolonged. The enhancement of AOM metabolism in rat liver by fasting, leading to increased liver DNA methylation, is different from that produced by chemical inducers, such as ethanol, where no increase in liver DNA methylation is observed.
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Affiliation(s)
- O S Sohn
- Division of Biochemical Pharmacology, American Health Foundation, Valhalla, NY 10595, USA
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Jenner AM, Timbrell JA. Influence of inducers and inhibitors of cytochrome P450 on the hepatotoxicity of hydrazine in vivo. Arch Toxicol 1994; 68:349-57. [PMID: 8092926 DOI: 10.1007/s002040050081] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Hydrazine hepatotoxicity in vivo, as manifested by triglyceride accumulation, depletion of ATP and reduced glutathione (GSH) was shown to be dose related. The effect of pretreatment of rats with various inhibitors and inducers of cytochrome P450 on these dose-response relationships was investigated. Pretreatment with the inhibitor piperonyl butoxide increased triglyceride accumulation whereas pretreatment with the inducers phenobarbital and beta-naphthoflavone (BNF) resulted in reduced triglyceride accumulation. Pretreatment with the inducers acetone and isoniazid also enhanced triglyceride accumulation. Only phenobarbital pretreatment also significantly reduced GSH and ATP depletion. A linear correlation was found between hepatic glutathione and ATP levels in non-pretreated animals given various doses of hydrazine. However, exponential relationships were found between hepatic triglycerides and both hepatic ATP and glutathione. The results suggest that i) the hepatotoxicity of hydrazine can be modulated by inducing or inhibiting particular isoenzymes of cytochrome P450, ii) ATP and GSH depletion may not be directly involved in the development of fatty liver.
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Affiliation(s)
- A M Jenner
- Toxicology Department, School of Pharmacy, University of London, UK
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17
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Jorquera R, Castonguay A, Schuller HM. Effects of age and ethanol on DNA single-strand breaks and toxicity induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone or n-nitrosodimethylamine in hamster and rat liver. Cancer Lett 1993; 74:175-81. [PMID: 8174101 DOI: 10.1016/0304-3835(93)90240-a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The effects of age and ethanol exposure on liver DNA single-strand breaks (SSB) and liver cell injury induced in hamsters and rats by a single equimolar dose (0.39 mmol/kg) of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) or N-nitrosodimethylamine (NDMA) were investigated. NNK induced more DNA SSB (by 10-50%) than NDMA in the liver of adult hamsters and rats, but similar differences were not observed in newborn animals. Nitrosamine-induced hepatic DNA damages was compared in newborn and adult animals. While newborn hamsters were less sensitive to NNK-induced DNA damage than adult hamsters, newborn rats were more sensitive to NDMA-induced DNA damage than adult rats. In utero ethanol exposure did not alter significantly the induction of hepatic DNA SSB by NNK or NDMA compared to newborn hamsters and rats. Interestingly, species differences in the extents of NNK-induced hepatic DNA SSB and toxicity were observed in ethanol-consuming adult hamsters and rats. Ethanol treatment of hamsters caused a significant reduction (by 35%) of the frequency of hepatic DNA SSB and a 3.5-fold enhancement of hepatotoxicity induced by NNK.
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Affiliation(s)
- R Jorquera
- Laboratory of Cancer Etiology and Chemoprevention, School of Pharmacy, Laval University, QC, Canada
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Schmitt FC, Estevao D, Kobayasi S, Curi P, de Camargo JL. Altered foci of hepatocytes in rats initiated with diethylnitrosamine after prolonged fasting. Food Chem Toxicol 1993; 31:629-36. [PMID: 8406239 DOI: 10.1016/0278-6915(93)90045-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The influence of fasting on the potential of diethylnitrosamine (DEN) to initiate liver carcinogenesis was tested in a medium-term assay using the development of putative preneoplastic altered foci of hepatocytes (AFH) as the endpoint. Male Wistar rats fasted for 48 hr were given a single ip injection of DEN (200 mg/kg body weight). Partial hepatectomies were carried out at wk 3 and the rats were killed at wk 8. Fasted rats exhibited a small increase in the numbers of AFH with glutathione S-transferase in the placental form and eosinophilic AFH when compared with non-fasted animals. However, after a 6-wk exposure to 0.05% sodium phenobarbital in the diet, there were no differences in the numbers of AFH between fasted and non-fasted animals. Fasting also increased DEN-dependent centrilobular cell necrosis and specifically drug metabolism as indicated in vivo by a decreased time of paralysis of the lower limbs induced by zoxazolamine (40 mg/kg body weight, ip) and by an unaltered sleeping time induced by sodium pentobarbital (40 mg/kg body weight, ip). The results indicate that although fasting during the initiation stage of carcinogenesis increases DEN hepatoxicity, it does not interfere quantitatively with the development of liver preneoplastic lesions.
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Affiliation(s)
- F C Schmitt
- Department of Pathology, UNESP Medical School, Botucatu, Brazil
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19
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Berman E, House DE, Allis JW, Simmons JE. Hepatotoxic interactions of ethanol with allyl alcohol or carbon tetrachloride in rats. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH 1992; 37:161-76. [PMID: 1522609 DOI: 10.1080/15287399209531663] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
To assess whether potential toxic interactions occur between ethanol and allyl alcohol or carbon tetrachloride following subacute, concurrent chemical exposure, male Fischer 344 rats, approximately 70 d of age, were given ethanol at 0, 0.05, 0.1, 0.2, or 0.5 ml/kg in corn oil daily by gavage for 14 d (ETOH group), or the same levels of ethanol with 21 mg allyl alcohol/kg (ALAC group), or the same levels of ethanol with 20 mg carbon tetrachloride/kg (CCL4 group). Hepatic response was assessed 24 h after the last dose. Interactions were evaluated by comparing the ETOH group with either the ALAC group or the CCL4 group using multivariate analysis of variance procedures. No statistically significant interaction was seen between the ETOH group and the ALAC group at the dosages used. Although an interaction between ethanol and carbon tetrachloride given simultaneously was not statistically significant, a small interactive effect on weight gain from d 0 to termination was apparent (p = .057). Exposure to ethanol alone resulted in a concentration-dependent decrease in absolute and relative liver weight, with a threshold between 0.05 and 0.1 ml/kg. There was no histopathological evidence of hepatic damage with ethanol alone, and no effect on hepatic cytochrome P-450 and glutathione levels or on serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALK). Exposure to allyl alcohol alone resulted in significant increases in absolute and relative liver weights, liver glutathione, and periportal hepatocellular vacuolar degeneration. Exposure to carbon tetrachloride alone resulted in significant increases in absolute and relative liver weight, serum levels of ALT, AST, and ALK, and centrilobular hepatocellular vacuolar degeneration and necrosis. These observations indicate that subacute, concurrent exposure of ethanol with carbon tetrachloride or allyl alcohol at ethanol levels comparable to those reported in gavage vehicles did not result in interactive toxicity.
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Affiliation(s)
- E Berman
- Developmental Toxicology Division, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711
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20
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Kasuga F, Inoue S, Asano T, Kumagai S. Effects of isopropanol on the development of inflammatory reactions in rats. Food Chem Toxicol 1992; 30:631-4. [PMID: 1521838 DOI: 10.1016/0278-6915(92)90198-t] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The effects of isopropanol on the development of inflammation were studied in rats. Isopropanol inhibited both the histamine-induced increase in cutaneous vascular permeability and the carrageenan-induced plasma exudation into the pleural cavity. The lipopolysaccharide-induced leucocyte emigration into the subcutaneous pouch was unaffected by isopropanol, but the leucocyte emigration of carrageenan-induced pleural inflammation was markedly inhibited by isopropanol. In contrast, when isopropanol was administered with an anti-inflammatory drug (indomethacin or dexamethasone), it enhanced the pleural inflammatory reaction. These results suggest that isopropanol may exert toxic effects through interference with the normal processes of inflammation and interaction with other agents that affect inflammatory reactions.
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Affiliation(s)
- F Kasuga
- Department of Biomedical Research on Food, National Institute of Health, Tokyo, Japan
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21
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Yonekura I, Matsumoto Y, Miura K, Sato A. Ethanol ingestion combined with lowered carbohydrate intake enhances the initiation of diethylnitrosamine liver carcinogenesis in rats. Nutr Cancer 1992; 17:171-8. [PMID: 1350084 DOI: 10.1080/01635589209514184] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
The effect of ethanol on the initiation of diethylnitrosamine- (DEN) induced liver carcinogenesis was investigated in rats. In the first experiment, eight-week-old male Wistar rats were maintained on four liquid diets: a basal diet (Group 1), a low-carbohydrate (low-CHO) diet (Group 2), a basal diet+ethanol (Group 3), or a low-CHO diet+ethanol (Group 4). After three weeks on these diets, 50 mg/kg of DEN was injected intraperitoneally. The plasma glutamic-oxaloacetic transaminase activity in Group 4 was higher 24 hours after DEN administration than in Groups 1 and 3. The plasma glutamic-pyruvic transaminase activity in Groups 3 and 4 was higher than in Groups 1 and 2. The number of gamma-glutamyltranspeptidase-positive foci per unit liver area 41 weeks after DEN administration was higher in Group 4 than in Group 1. The area of gamma-glutamyltranspeptidase-positive foci was greater in Groups 2 and 4 than in Group 1. In the second experiment, Groups 1 and 4 were given DEN orally (25 or 75 mg/kg). Plasma glutamic-oxaloacetic transaminase and glutamic-pyruvic transaminase activities 24 hours after DEN administration were significantly higher in Group 4 than in Group 1, but only when the dose of DEN was 75 mg/kg. In contrast, the number and area of placental glutathione S-transferase-positive foci per unit liver area were greater in Group 4 than in Group 1 only after 25 mg/kg of DEN. Thus the severity of hepatotoxicity and the incidence of precancerous liver lesions were not necessarily correlated. These findings together indicate that a combination of ethanol and a low-CHO diet enhances DEN-induced liver carcinogenesis in rats by increasing the bioactivation of DEN in the liver.
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Affiliation(s)
- I Yonekura
- Department of Environmental Health, Medical University of Yamanashi, Japan
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22
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Abstract
Until two decades ago, dietary deficiencies were considered to be the major reason why alcoholics developed liver disease. As the overall nutrition of the population improved, more emphasis was placed on secondary malnutrition. Direct hepatotoxic effects of ethanol were also established, some of which were linked to redox changes produced by reduced nicotinamide adenine dinucleotide (NADH) generated via the alcohol dehydrogenase (ADH) pathway. It was also determined that ethanol can be oxidized by a microsomal ethanol oxidizing system (MEOS) involving cytochrome P-450: the newly discovered ethanol-inducible cytochrome P-450 (P-450IIE1) contributes to ethanol metabolism, tolerance, energy wastage (with associated weight loss), and the selective hepatic perivenular toxicity of various xenobiotics. P-450 induction also explains depletion (and enhanced toxicity) of nutritional factors such as vitamin A. Even at the early fatty-liver stage, alcoholics commonly have a very low hepatic concentration of vitamin A. Ethanol administration in animals was found to depress hepatic levels of vitamin A, even when administered with diets containing large amounts of the vitamin, reflecting, in part, accelerated microsomal degradation through newly discovered microsomal pathways of retinol metabolism, inducible by either ethanol or drug administration. The hepatic depletion of vitamin A was strikingly exacerbated when ethanol and other drugs were given together, mimicking a common clinical occurrence. Hepatic retinoid depletion was found to be associated with lysosomal lesions and decreased detoxification of chemical carcinogens. To alleviate these adverse effects, as well as to correct problems of night blindness and sexual inadequacies, the alcoholic patient should be provided with vitamin A supplementation. Such therapy, however, is complicated by the fact that in excessive amounts vitamin A is hepatotoxic, an effect exacerbated by long-term ethanol consumption. This results in striking morphologic and functional alterations of the mitochondria with leakage of mitochondrial enzymes, hepatic necrosis, and fibrosis. Thus, treatment with vitamin A and other nutritional factors (such as proteins) is beneficial but must take into account a narrowed therapeutic window in alcoholics who have increased needs for such nutrients, but also display an enhanced susceptibility to their adverse effects. Massive doses of choline also exerted some toxic effects and failed to prevent the development of alcoholic cirrhosis. Acetaldehyde (the metabolite produced from ethanol by either ADH or MEOS) impairs hepatic oxygen utilization and forms protein adducts, resulting in antibody production, enzyme inactivation, and decreased DNA repair. It also enhances pyridoxine and perhaps folate degradation and stimulates collagen production by the vitamin A storing cells (lipocytes) and myofibroblasts.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- C S Lieber
- Section of Liver Disease and Nutrition, Bronx VA Medical Center, New York 10468
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23
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Abstract
Until two decades ago, dietary deficiencies were considered to be the only reason for alcoholics to develop liver disease. As the overall nutrition of the population improved, more emphasis was placed on secondary malnutrition and direct hepatotoxic effects of ethanol were established. Ethanol is hepatotoxic through redox changes produced by the NADH generated in its oxidation via the alcohol dehydrogenase pathway, which in turn affects the metabolism of lipids, carbohydrates, proteins, and purines. Ethanol is also oxidized in liver microsomes by an ethanol-inducible cytochrome P-450 (P-450IIE1) that contributes to ethanol metabolism and tolerance, and activates xenobiotics to toxic radicals thereby explaining increased vulnerability of the heavy drinker to industrial solvents, anesthetic agents, commonly prescribed drugs, over-the-counter analgesics, chemical carcinogens, and even nutritional factors such as vitamin A. In addition, ethanol depresses hepatic levels of vitamin A, even when administered with diets containing large amounts of the vitamin, reflecting, in part, accelerated microsomal degradation through newly discovered microsomal pathways of retinol metabolism, inducible by either ethanol or drug administration. The hepatic depletion of vitamin A is strikingly exacerbated when ethanol and other drugs were given together, mimicking a common clinical occurrence. Microsomal induction also results in increased production of acetaldehyde. Acetaldehyde, in turn, causes injury through the formation of protein adducts, resulting in antibody production, enzyme inactivation, decreased DNA repair, and alterations in microtubules, plasma membranes and mitochondria with a striking impairment of oxygen utilization. Acetaldehyde also causes glutathione depletion and lipid peroxidation, and stimulates hepatic collagen production by the vitamin A storing cells (lipocytes) and myofibroblasts.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- C S Lieber
- Alcohol Research and Treatment Center, Department of Veterans Affairs Medical Center, Bronx, NY 10468
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Brady JF, Xiao F, Wang MH, Li Y, Ning SM, Gapac JM, Yang CS. Effects of disulfiram on hepatic P450IIE1, other microsomal enzymes, and hepatotoxicity in rats. Toxicol Appl Pharmacol 1991; 108:366-73. [PMID: 1850173 DOI: 10.1016/0041-008x(91)90125-x] [Citation(s) in RCA: 96] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Disulfiram, widely used in avoidance therapy for alcohol abuse, has been shown to have protective effects against chemically induced toxicity and carcinogenesis. The purpose of this work was to elucidate the biochemical mechanisms of this protective action by examining its effects on cytochrome P450IIE1 and other related microsomal enzyme activities. When a dose of disulfiram was given intragastrically to rats, a very rapid decrease of N-nitrosodimethylamine (NDMA) demethylase activity, possibly due to the inactivation of P450IIE1, was seen. The loss of P450IIE1 protein from the microsomal membrane was observed at 18 hr after receiving disulfiram, but not within the first 5 hr after the treatment. P450IIB1, on the other hand, was induced markedly between 15 and 72 hr after the disulfiram treatment. The treatment, however, caused only moderate changes in some other P450 isozymes. Carbon disulfide, a putative metabolite of disulfiram, produced similar effects on P450IIE1, but with shorter duration. Carbon disulfide, however, did not induce P450IIB1. Diethyldithiocarbamate, a reductive product of disulfiram, was an inhibitor of P450IIE1 activity in vitro, and upon preincubation with microsomes, it produced an NADPH-dependent inactivation of NDMA demethylase activity. The results suggest that this or other metabolites of disulfiram are inhibitors of P450IIE1 and are responsible for the inactivation of P450IIE1 in vivo. Hepatotoxicity of NDMA or CCI4 in rats was blocked by pretreatment with disulfiram. The present work demonstrates that P450IIE1 was inhibited and inactivated by disulfiram, and this mechanism can account for many of the reported inhibitory actions of disulfiram against chemically induced toxicity and carcinogenesis.
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Affiliation(s)
- J F Brady
- Department of Chemical Biology and Pharmacognosy, College of Pharmacy, Rutgers University, Piscataway, New Jersey 08855-0789
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25
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Brady JF, Wang MH, Hong JY, Xiao F, Li Y, Yoo JS, Ning SM, Lee MJ, Fukuto JM, Gapac JM. Modulation of rat hepatic microsomal monooxygenase enzymes and cytotoxicity by diallyl sulfide. Toxicol Appl Pharmacol 1991; 108:342-54. [PMID: 2017758 DOI: 10.1016/0041-008x(91)90123-v] [Citation(s) in RCA: 106] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Diallyl sulfide (DAS) and other organosulfur compounds inhibit chemically induced carcinogenic and toxic responses in rodent model systems. A possible mechanism of action is the inhibition of the hepatic cytochrome P450IIE1-dependent bioactivation of the procarcinogens and protoxicants. Previous work showed competitive inhibition by DAS of N-nitrosodimethylamine (NDMA) demethylase activity in vitro, and a reduction in the microsomal level of P450IIE1 after in vivo treatment with DAS. The present studies demonstrated a time- and dose-dependent decrease of hepatic microsomal P450IIE1 activity, induction of P450IIB1 and pentoxyresorufin dealkylase activity, and moderate induction of ethoxyresorufin dealkylase activity by oral DAS treatment. DAS treatment elevated P450IIB1 mRNA but had no effect on P450IIE1 mRNA. Treatment with putative metabolites of DAS, diallyl sulfoxide and diallyl sulfone, led to similar modulations in monooxygenase activities, but the decrease of P450IIE1 activity by the sulfone occurred more rapidly. In studies in vitro, diallyl sulfone caused a metabolism-dependent inactivation of P450IIE1, but such inactivation was not observed with DAS or diallyl sulfoxide. The profile of microsomal testosterone metabolism after DAS treatment indicated an enhancement of P450IIB1-dependent 16 beta-hydroxylase activity, and a decrease in 6 beta-hydroxytestosterone production possibly related to a lower level of P450IIIA1 or IIIA2. When rats were subjected to a 48-hr fast and DAS treatment, the starvation-induced microsomal P450IIE1 level was decreased by DAS. Inhibition of hepatotoxicity due to exposure to P450IIE1 substrates, CCl4 and NDMA, by DAS was observed under a variety of treatment schedules.
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Affiliation(s)
- J F Brady
- Department of Chemical Biology and Pharmacognosy, College of Pharmacy, Rutgers University, Piscataway, New Jersey 08855-0789
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26
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Simmons JE, Allis JW, Grose EC, Seely JC, Robinson BL, Berman E. Assessment of the hepatotoxicity of acute and short-term exposure to inhaled p-xylene in F-344 rats. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH 1991; 32:295-306. [PMID: 2002513 DOI: 10.1080/15287399109531483] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Due to the ubiquitous presence of p-xylene in air and the existing uncertainty regarding its hepatotoxic potential, we examined the effect of acute and short-term exposure to inhaled p-xylene on the liver. Male F-344 rats were exposed to 0 or to 1600 ppm p-xylene, 6 h/d, for 1 or 3 d. Exposure to inhaled p-xylene caused no histopathological evidence of hepatic damage and had little or no effect on the serum levels of aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, ornithine carbamyl transferase, alkaline phosphatase, and total bilirubin. Exposure to p-xylene for 1 or 3 d resulted in an increase in relative liver weight on d 1 post-exposure. The concentration of hepatic cytochrome P-450 was increased by both p-xylene exposure regimens on d 1 postexposure and had returned to control levels by d 3 following the single p-xylene exposure and by d 2 following the 3-d exposure. These observations provide consistent evidence that acute and short-term exposure to 1600 ppm p-xylene by inhalation did not produce overt hepatotoxicity but resulted in a significant increase in the concentration of hepatic cytochrome P-450, the principal enzyme system involved in the metabolic biotransformation of xenobiotics.
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Affiliation(s)
- J E Simmons
- Health Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711
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27
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Imaoka S, Yamaguchi Y, Funae Y. Induction and regulation of cytochrome P450 K-5 (lauric acid hydroxylase) in rat renal microsomes by starvation. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1036:18-23. [PMID: 2223822 DOI: 10.1016/0304-4165(90)90208-e] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The effects of starvation on rat renal cytochrome P-450s were studied. The content of spectrally measured cytochrome P-450 in the renal microsomes of male rats increased 2-fold with 72 h starvation, but cytochrome b5 and NADPH-cytochrome P-450 reductase were not induced. 7-Ethoxycoumarin O-dealkylation and aniline hydroxylation activities of the renal microsomes of control male rats were very low but were induced 2.5-3-fold by 72 h starvation. Aminopyrine N-demethylation and lauric acid hydroxylation activities were induced 1.5-2-fold by 72 h starvation. The changes in catalytic activities suggested that the contents of individual cytochrome P-450s in the renal microsomes were altered by starvation. The contents of some cytochrome P-450s were measured by Western blotting. P450 DM (P450IIE1), a typical form of cytochrome P-450 induced by starvation in rat liver, was barely detected in rat kidney and was induced 2-fold by 72 h starvation. P450 K-5, a typical renal cytochrome P-450 and lauric acid hydroxylase, accounted for 81% of the spectrally measured cytochrome P-450 in the renal microsomes of control male rats and was induced 2-fold by 72 h starvation. P450 K-5 was not induced in rat kidney by treatment with chemicals such as acetone or clofibrate. The renal microsomes of male rats contained 6-times as much P450 K-5 as those of female rats. These results suggest that P450 K-5 is regulated by an endocrine factor.
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Affiliation(s)
- S Imaoka
- Laboratory of Chemistry, Osaka City University Medical School, Japan
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28
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Imaoka S, Terano Y, Funae Y. Changes in the amount of cytochrome P450s in rat hepatic microsomes with starvation. Arch Biochem Biophys 1990; 278:168-78. [PMID: 2321956 DOI: 10.1016/0003-9861(90)90245-t] [Citation(s) in RCA: 100] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The effects of starvation on the composition of 12 different cytochrome P450s in rat hepatic microsomes were studied with a specific antibody. Changes in the metabolic activity of the microsomes were studied at the same time. P450 DM (P450j) was induced 2.5-fold by a 48-h starvation and its increase reflected the increase of metabolic activity of hepatic microsomes toward aniline, 7-ethoxycoumarin, and N-nitrosodimethylamine. P450 K-5, the major renal cytochrome P450 in untreated male rat, was also induced 2.5-fold by a 48-h starvation. P450 UT-2 (P450h) and P450 UT-5 (P450g), typical male-specific forms, decreased with starvation. P450 UT-2 had high testosterone 2 alpha- and 16 alpha-hydroxylation activities. These activities of hepatic microsomes were reduced with the decrease in P450 UT-2. P450 PB-1, testosterone 6 beta-hydroxylase, was increased time-dependently by starvation. P450 UT-4 (RLM2), a minor male-specific form, was not changed by starvation. P450 PB-2 (P450k), present in both sexes, was changed little by starvation. P450 PB-4 (P450b) and P450 PB-5 (P450e) are strongly induced in rat liver by phenobarbital in coordinate fashion. Starvation increased P450 PB-4 12-fold but reduced P450 PB-5 to 22% of the control level. P450 MC-1 (P450d) was decreased by starvation. P450 MC-5 (P450c) was barely detected in control rats and was not changed by starvation. P450 IF-3 (P450a), rich in immature rats, was increased by starvation, accompanied by an increase in testosterone 7 alpha-hydroxylation activity in the hepatic microsomes. We further investigated whether new cytochrome P450s appeared upon starvation by comparison of chromatographic profiles of cytochrome P450 from starved rats with those of cytochrome P450 from control rats using HPLC. Three new cytochrome P450s were detected in the starved rats. These cytochrome P450s were purified to homogeneity. One of them was P450 DM, judging from spectral properties, catalytic activity, and the NH2-terminal sequence. The two other forms were designated P450 3b and 4b. The minimum molecular weights of P450 3b and 4b were 53,000 and 52,000, respectively, and their CO-reduced absorption maxima were at 449 and 452 nm, respectively. P450 3b metabolized aminopyrine, N-nitrosodimethylamine, 7-ethoxycoumarin, and lauric acid, but with low activity. P450 4b was efficient in lauric acid omega- and (omega-1)-hydroxylation only. The spectral properties, catalytic activity, peptide map, and NH2-terminal sequence of P450 4b agreed with those of P450 K-5. P450 3b was a new cytochrome P450, judged by these criteria.
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Affiliation(s)
- S Imaoka
- Laboratory of Chemistry, Osaka City University Medical School, Japan
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29
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Abstract
Ethanol is hepatotoxic through redox changes produced by the NADH generated in its oxidation via the alcohol dehydrogenase pathway, which in turn affects the metabolism of lipids, carbohydrates, proteins and purines. Ethanol is also oxidized in liver microsomes by an ethanol-inducible cytochrome P-450 (P-450IIE1) which contributes to ethanol metabolism and tolerance, and activates xenobiotics to toxic radicals thereby explaining increased vulnerability of the heavy drinker to industrial solvents, anesthetic agents, commonly prescribed drugs, over-the-counter analgesics, chemical carcinogens and even nutritional factors such as vitamin A. Induction also results in energy wastage and increased production of acetaldehyde. Acetaldehyde, in turn, causes injury through the formation of protein adducts, resulting in antibody production, enzyme inactivation, decreased DNA repair, and alterations in microtubules, plasma membranes and mitochondria with a striking impairment of oxygen utilization. Acetaldehyde also causes glutathione depletion and lipid peroxidation, and stimulates hepatic collagen synthesis, thereby promoting fibrosis.
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Affiliation(s)
- C S Lieber
- Alcohol Research and Treatment Center, Bronx VA Medical Center, New York
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30
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Yang CS, Yoo JS, Ishizaki H, Hong JY. Cytochrome P450IIE1: roles in nitrosamine metabolism and mechanisms of regulation. Drug Metab Rev 1990; 22:147-59. [PMID: 2272285 DOI: 10.3109/03602539009041082] [Citation(s) in RCA: 280] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- C S Yang
- Department of Chemical Biology and Pharmacognosy College of Pharmacy, Rutgers University, Piscataway, New Jersey 08855-0789
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31
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Flatt PR, Bass SL, Ayrton AD, Trinick J, Ioannides C. Metabolic activation of chemical carcinogens by hepatic preparations from streptozotocin-treated rats. Diabetologia 1989; 32:135-9. [PMID: 2524416 DOI: 10.1007/bf00505186] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The effect of insulin-dependent diabetes on the hepatic microsomal activation of chemical carcinogens to mutagenic intermediates in the Ames test was investigated in rats pretreated with streptozotocin. In order to discern between the effects of streptozotocin itself and that of the resulting diabetes, groups of streptozotocin-treated rats received either nicotinamide simultaneously with the diabetogenic agent to prevent the onset of diabetes or daily treatment with insulin in order to antagonise the effects of diabetes. The activation of two nitrosamines, nitrosopiperidine and nitrosopyrrolidine was markedly increased following treatment of the animals with streptozotocin, the effect being preventable by nicotinamide and effectively antagonised by insulin. A similar increase in mutagenic response was also seen when Glu-P-1, a carcinogen generated during the cooking of proteinaceous food, was employed as the mutagen. In contrast, the diabetic rats were less efficient than control animals in activating the aromatic amine 2-aminofluorene to mutagenic intermediates. Concomitant administration of nicotinamide with streptozotocin prevented the decrease in mutagenicity, and daily treatment of diabetic rats with insulin partially restored mutagenic response to control levels. Streptozotocin-induced diabetes had no effect on the mutagenicity of 4-aminobiphenyl and the two polycyclic aromatic hydrocarbons, benzo(a)pyrene and 3-methylcholanthrene. The present findings clearly illustrate that diabetes modulates the metabolic activation of carcinogenic chemicals, the effect being dependent on the nature of the carcinogen.
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Affiliation(s)
- P R Flatt
- Biochemistry Department, University of Surrey, UK
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32
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Abstract
There is a great deal of epidemiological evidence indicating that chronic, excessive alcohol consumption is a major risk factor for cancers in humans. However, the experimental basis for the increased cancer risk associated with alcohol intake is not clear. Since it appears that ethanol alone is not carcinogenic, ethanol effects must be explained in terms of its modifying the actions of other causal agents. Current studies indicate that ethanol and its congeners may act as tumor promoters, thereby enhancing the effect of initiating carcinogens from the environment. Available evidence also shows that ethanol is immunosuppressive. Clearly, cirrhosis due to high, prolonged alcohol intake is an indicator of the immunosuppressive effects of ethanol. It is less clear that more moderate intakes of alcohol could have as profound an effect on immune systems. However, changes do occur yielding alterations in lymphocyte sensitivity to alcohol in vitro and in cell development, as shown by increased NK cell function at low concentrations. Since other conditions, such as cytotoxic drugs which suppress cellular immune functions, are clearly associated with increased cancer risk. It is intriguing to think that prolonged exposure to ethanol-induced immunosuppression may be a cofactor in the promotion of cancer. The tumor promotion may take place via a variety of mechanisms as discussed in this paper, including reduced host defenses by direct effects of ethanol, its metabolites, and/or malnutrition. It may be beneficial to test methods for immunostimulation in prolonged alcohol abusers, where cessation of use is unsuccessful or residual immunosuppression remains, to reduce the risk of development or growth of initiated tumors.
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Affiliation(s)
- S I Mufti
- Department of Pharmacology-Toxicology, College of Pharmacy, University of Arizona, Tucson 85724
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33
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Ioannides C, Bass SL, Ayrton AD, Trinick J, Walker R, Flatt PR. Streptozotocin-induced diabetes modulates the metabolic activation of chemical carcinogens. Chem Biol Interact 1988; 68:189-202. [PMID: 2975197 DOI: 10.1016/0009-2797(88)90016-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The effect of chemically-induced diabetes on the hepatic microsomal mixed-function oxidase system and the activation of chemical carcinogens was investigated in animals treated with streptozotocin (STZ). In order to distinguish between the effects of the diabetogenic chemical per se and that of the diabetic state, groups of STZ-treated animals received either nicotinamide simultaneously with STZ to prevent the onset of diabetes, or daily treatment with insulin in order to reverse the effects of diabetes. STZ-treated animals exhibited higher pentoxyresorufin O-dealkylase, ethoxy-resorufin O-deethylase, ethoxycoumarin O-deethylase, aniline p-hydroxylase and NADPH-cytochrome c reductase activities; similarly, increases were seen in cytochrome P-450 and b5 levels. All of these effects were prevented by nicotinamide and, at least partly, antagonised by insulin therapy. Treatment of animals with STZ markedly increased the activation, by liver microsomes in vitro, of Trp-P-1 and Trp-P-2 to mutagens, the effect being totally preventable by nicotinamide and successfully antagonised with insulin therapy. The diabetic animals were similarly more efficient in activating MeIQ but the effect was not preventable by nicotinamide or reversed by insulin. In contrast no changes were seen in the activation of IQ and only a modest increase in the case of MeIQx. It is concluded that diabetes may modulate the metabolic activation of some chemical carcinogens, presumably by changing the ratio of the various cytochrome P-450 isoenzymes.
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Affiliation(s)
- C Ioannides
- Department of Biochemistry, University of Surrey, Guildford, U.K
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Patten CJ, Ning SM, Lu AY, Yang CS. Acetone-inducible cytochrome P-450: purification, catalytic activity, and interaction with cytochrome b5. Arch Biochem Biophys 1986; 251:629-38. [PMID: 3800390 DOI: 10.1016/0003-9861(86)90373-5] [Citation(s) in RCA: 116] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
A procedure was developed for the purification of an acetone-inducible form of cytochrome P-450 (P-450ac) to electrophoretical homogeneity from liver microsomes of acetone-treated rats. The P-450ac preparation containing 16.0 to 16.5 nmol P-450/mg protein moved as a single protein band with an estimated molecular weight of 52,000 upon gel electrophoresis in the presence of sodium dodecyl sulfate. The ferric P-450ac showed an absorption maximum at 394 nm at 25 degrees C, suggesting that it exists mainly in the high-spin form. It also existed in the low-spin form, especially at lower temperatures, as indicated by the absorption maximum in the 412-nm region. Upon reconstitution with NADPH: cytochrome P-450 reductase and phospholipid, P-450ac efficiently catalyzed both the demethylation and denitrosation of N-nitrosodimethylamine (NDMA) showing Vmax values of 23.8 and 2.3 nmol min-1 nmol P-450-1, respectively. The catalytic activity of P-450ac was greatly affected by cytochrome b5 which decreased the Km values of these reactions by a factor of 10 and increased the Vmax values. Cytochrome b5 appeared to interact with P-450 at a molar ratio of 1:1 and an intact cytochrome b5 structure was required for such interaction. Among the substrates studied, the demethylation of NDMA was affected the most by cytochrome b5 and showed the highest rate. P-450ac also catalyzed the oxygenation of N-nitrosomethylethylamine and aniline and the activity was enhanced slightly by cytochrome b5. Cytochrome b5 did not enhance the P-450ac-catalyzed metabolism of other drug substrates such as benzphetamine, aminopyrine, and ethylmorphine. P-450ac appeared to be similar in property to the previously studied rat P-450et (ethanol-inducible), rat P-450j (isoniazid-inducible), and rabbit P-450LM3a (ethanol-inducible). These P-450 species represent a new class of P-450 isozymes that are important in the metabolism of many endobiotics and xenobiotics.
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Abstract
The metabolism of certain compounds by rat hepatic microsomal preparations obtained from acetone-treated rats is greater than that measured in microsomes obtained from control rats. Since the lipid composition of membranes can significantly influence metabolism catalyzed by membrane-bound enzymes, studies were conducted in order to determine whether acetone-induced alterations in microsomal metabolism are associated with changes in the lipid composition of these membranes. Phospholipid and cholesterol concentrations were measured in extracts of rat liver microsomes obtained from rats treated with acetone, sodium phenobarbital, or vehicle. Acetone treatment did not alter the phospholipid and cholesterol content of the microsomes, whereas sodium phenobarbital (positive control) caused a significant decrease in cholesterol content/mg microsomal protein. These data indicate that acetone-induced alterations in microsomal metabolism may not be attributed to changes in the phospholipid and cholesterol content of the microsomes.
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